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13 pages, 1027 KiB

Open AccessArticle

Somatic Embryogenesis Initiation in Sugi (Japanese Cedar, Cryptomeria japonica D. Don): Responses from Male-Fertile, Male-Sterile, and Polycross-Pollinated-Derived Seed Explants

by Tsuyoshi E. Maruyama, Saneyoshi Ueno, Yoshihisa Hosoi, Shin-Ichi Miyazawa, Hideki Mori, Takumi Kaneeda, Yukiko Bamba, Yukiko Itoh, Satoko Hirayama, Kiyohisa Kawakami and Yoshinari Moriguchi

Plants 2021, 10(2), 398; https://doi.org/10.3390/plants10020398 - 19 Feb 2021

Cited by 6 | Viewed by 2451

Abstract

This study aimed to obtain information from several embryogenic cell (EC) genotypes analyzing the factors that affect somatic embryogenesis (SE) initiation in sugi (Cryptomeria japonica, Cupressaceae) to apply them in the improvement of protocols for efficient induction of embryogenic cell lines (ECLs). [...] Read more.

This study aimed to obtain information from several embryogenic cell (EC) genotypes analyzing the factors that affect somatic embryogenesis (SE) initiation in sugi (Cryptomeria japonica, Cupressaceae) to apply them in the improvement of protocols for efficient induction of embryogenic cell lines (ECLs). The results of several years of experiments including studies on the influence of initial explant, seed collection time, and explant genotype as the main factors affecting SE initiation from male-fertile, male-sterile, and polycross-pollinated-derived seeds are described. Initiation frequencies depending on the plant genotype varied from 1.35 to 57.06%. The best induction efficiency was achieved when seeds were collected on mid-July using the entire megagametophyte as initial explants. The extrusion of ECs started approximately after 2 weeks of culture, and the establishment of ECLs was observed mostly 4 weeks after extrusion on media with or without plant growth regulators (PGRs). Subsequently, induced ECLs were maintained and proliferated on media with PGRs by 2–3-week-interval subculture routines. Although, the initial explant, collection time, and culture condition played important roles in ECL induction, the genotype of the plant material of sugi was the most influential factor in SE initiation. Full article

(This article belongs to the Special Issue Advances in Plant Regeneration)

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15 pages, 2218 KiB

Open AccessArticle

Polyamine Metabolism Is Involved in the Direct Regeneration of Shoots from Arabidopsis Lateral Root Primordia

by Nikolett Kaszler, Péter Benkő, Dóra Bernula, Ágnes Szepesi, Attila Fehér and Katalin Gémes

Plants 2021, 10(2), 305; https://doi.org/10.3390/plants10020305 - 05 Feb 2021

Cited by 12 | Viewed by 3367

Abstract

Plants can be regenerated from various explants/tissues via de novo shoot meristem formation. Most of these regeneration pathways are indirect and involve callus formation. Besides plant hormones, the role of polyamines (PAs) has been implicated in these processes. Interestingly, the lateral root primordia [...] Read more.

Plants can be regenerated from various explants/tissues via de novo shoot meristem formation. Most of these regeneration pathways are indirect and involve callus formation. Besides plant hormones, the role of polyamines (PAs) has been implicated in these processes. Interestingly, the lateral root primordia (LRPs) of Arabidopsis can be directly converted to shoot meristems by exogenous cytokinin application. In this system, no callus formation takes place. We report that the level of PAs, especially that of spermidine (Spd), increased during meristem conversion and the application of exogenous Spd improved its efficiency. The high endogenous Spd level could be due to enhanced synthesis as indicated by the augmented relative expression of PA synthesis genes (AtADC1,2, AtSAMDC2,4, AtSPDS1,2) during the process. However, the effect of PAs on shoot meristem formation might also be dependent on their catabolism. The expression of Arabidopsis POLYAMINE OXIDASE 5 (AtPAO5) was shown to be specifically high during the process and its ectopic overexpression increased the LRP-to-shoot conversion efficiency. This was correlated with Spd accumulation in the roots and ROS accumulation in the converting LRPs. The potential ways how PAO5 may influence direct shoot organogenesis from Arabidopsis LRPs are discussed. Full article

(This article belongs to the Special Issue Advances in Plant Regeneration)

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15 pages, 1696 KiB

Open AccessArticle

Differential Expression Profiling Reveals Stress-Induced Cell Fate Divergence in Soybean Microspores

by Brett Hale, Callie Phipps, Naina Rao, Asela Wijeratne and Gregory C. Phillips

Plants 2020, 9(11), 1510; https://doi.org/10.3390/plants9111510 - 07 Nov 2020

Cited by 12 | Viewed by 3325

Abstract

Stress-induced microspore embryogenesis is a widely employed method to achieve homozygosity in plant breeding programs. However, the molecular mechanisms that govern gametophyte de- and redifferentiation are understood poorly. In this study, RNA-Seq was used to evaluate global changes across the microspore transcriptome of [...] Read more.

Stress-induced microspore embryogenesis is a widely employed method to achieve homozygosity in plant breeding programs. However, the molecular mechanisms that govern gametophyte de- and redifferentiation are understood poorly. In this study, RNA-Seq was used to evaluate global changes across the microspore transcriptome of soybean (Glycine max [L.] Merrill) as a consequence of pretreatment low-temperature stress. Expression analysis revealed more than 20,000 differentially expressed genes between treated and control microspore populations. Functional enrichment illustrated that many of these genes (e.g., those encoding heat shock proteins and cytochrome P450s) were upregulated to maintain cellular homeostasis through the mitigation of oxidative damage. Moreover, transcripts corresponding to saccharide metabolism, vacuolar transport, and other pollen-related developmental processes were drastically downregulated among treated microspores. Temperature stress also triggered cell wall modification and cell proliferation—characteristics that implied putative commitment to an embryonic pathway. These findings collectively demonstrate that pretreatment cold stress induces soybean microspore reprogramming through suppression of the gametophytic program while concomitantly driving sporophytic development. Full article

(This article belongs to the Special Issue Advances in Plant Regeneration)

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22 pages, 2239 KiB

Open AccessArticle

Trichostatin A Affects Developmental Reprogramming of Bread Wheat Microspores towards an Embryogenic Route

by Ana María Castillo, Isabel Valero-Rubira, María Ángela Burrell, Sandra Allué, María Asunción Costar and María Pilar Vallés

Plants 2020, 9(11), 1442; https://doi.org/10.3390/plants9111442 - 26 Oct 2020

Cited by 15 | Viewed by 3216

Abstract

Microspores can be developmentally reprogrammed by the application of different stress treatments to initiate an embryogenic pathway leading to the production of doubled haploid (DH) plants. Epigenetic modifications are involved in cell reprogramming and totipotency in response to stress. To increase microspore embryogenesis [...] Read more.

Microspores can be developmentally reprogrammed by the application of different stress treatments to initiate an embryogenic pathway leading to the production of doubled haploid (DH) plants. Epigenetic modifications are involved in cell reprogramming and totipotency in response to stress. To increase microspore embryogenesis (ME) efficiency in bread wheat, the effect of the histone deacetylase inhibitor trichostatin A (TSA) has been examined in two cultivars of wheat with different microspore embryogenesis response. Diverse strategies were assayed using 0–0.4 µM TSA as a single induction treatment and after or simultaneously with cold or mannitol stresses. The highest efficiency was achieved when 0.4 µM TSA was applied to anthers for 5 days simultaneously with a 0.7 M mannitol treatment, producing a four times greater number of green DH plants than mannitol. Ultrastructural studies by transmission electron microscopy indicated that mannitol with TSA and mannitol treatments induced similar morphological changes in early stages of microspore reprogramming, although TSA increased the number of microspores with ’star-like’ morphology and symmetric divisions. The effect of TSA on the transcript level of four ME marker genes indicated that the early signaling pathways in ME, involving the TaTDP1 and TAA1b genes, may be mediated by changes in acetylation patterns of histones and/or other proteins. Full article

(This article belongs to the Special Issue Advances in Plant Regeneration)

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11 pages, 1505 KiB

Open AccessArticle

Improving the Efficiency of Adventitious Shoot Induction and Somatic Embryogenesis via Modification of WUSCHEL and LEAFY COTYLEDON 1

by Miho Ikeda, Mikiya Takahashi, Sumire Fujiwara, Nobutaka Mitsuda and Masaru Ohme-Takagi

Plants 2020, 9(11), 1434; https://doi.org/10.3390/plants9111434 - 25 Oct 2020

Cited by 7 | Viewed by 3283

Abstract

The induction of adventitious organs, such as calli, shoots, and somatic embryos, in tissue culture is a useful technique for plant propagation and genetic modification. In recent years, several genes have been reported to be adventitious organ inducers and proposed to be useful [...] Read more.

The induction of adventitious organs, such as calli, shoots, and somatic embryos, in tissue culture is a useful technique for plant propagation and genetic modification. In recent years, several genes have been reported to be adventitious organ inducers and proposed to be useful for industrial applications. Even though the Arabidopsis (Arabidopsis thaliana) WUSCHEL (WUS) and LEAFY COTYLEDON 1 (LEC1) genes can induce adventitious organ formation in Arabidopsis without phytohormone treatment, further improvement is desired. Here, we show that modifying the transcriptional repression/activation activities of WUS and LEC1 improves the efficiency of adventitious organ formation in Arabidopsis. Because WUS functions as a transcriptional repressor during the induction of adventitious organs, we fused it to an artificial strong repression domain, SUPERMAN REPRESSION DOMAIN X (SRDX). Conversely, we fused the strong transcriptional activation domain VP16 from herpes simplex virus to LEC1. Upon overexpression of the corresponding transgenes, we succeeded in improving the efficiency of adventitious organ induction. Our results show that the modification of transcriptional repression/activation activity offers an effective method to improve the efficiency of adventitious organ formation in plants. Full article

(This article belongs to the Special Issue Advances in Plant Regeneration)

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15 pages, 4255 KiB

Open AccessFeature PaperArticle

Molecular and Biochemical Differences in Leaf Explants and the Implication for Regeneration Ability in Rorippa aquatica (Brassicaceae)

by Rumi Amano, Risa Momoi, Emi Omata, Taiga Nakahara, Kaori Kaminoyama, Mikiko Kojima, Yumiko Takebayashi, Shuka Ikematsu, Yuki Okegawa, Tomoaki Sakamoto, Hiroyuki Kasahara, Hitoshi Sakakibara, Ken Motohashi and Seisuke Kimura

Plants 2020, 9(10), 1372; https://doi.org/10.3390/plants9101372 - 15 Oct 2020

Cited by 2 | Viewed by 2760

Abstract

Plants have a high regeneration capacity and some plant species can regenerate clone plants, called plantlets, from detached vegetative organs. We previously outlined the molecular mechanisms underlying plantlet regeneration from Rorippa aquatica (Brassicaceae) leaf explants. However, the fundamental difference between the plant species [...] Read more.

Plants have a high regeneration capacity and some plant species can regenerate clone plants, called plantlets, from detached vegetative organs. We previously outlined the molecular mechanisms underlying plantlet regeneration from Rorippa aquatica (Brassicaceae) leaf explants. However, the fundamental difference between the plant species that can and cannot regenerate plantlets from vegetative organs remains unclear. Here, we hypothesized that the viability of leaf explants is a key factor affecting the regeneration capacity of R. aquatica. To test this hypothesis, the viability of R. aquatica and Arabidopsis thaliana leaf explants were compared, with respect to the maintenance of photosynthetic activity, senescence, and immune response. Time-course analyses of photosynthetic activity revealed that R. aquatica leaf explants can survive longer than those of A. thaliana. Endogenous abscisic acid (ABA) and jasmonic acid (JA) were found at low levels in leaf explant of R. aquatica. Time-course transcriptome analysis of R. aquatica and A. thaliana leaf explants suggested that senescence was suppressed at the transcriptional level in R. aquatica. Application of exogenous ABA reduced the efficiency of plantlet regeneration. Overall, our results propose that in nature, plant species that can regenerate in nature can survive for a long time. Full article

(This article belongs to the Special Issue Advances in Plant Regeneration)

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15 pages, 3565 KiB

Open AccessArticle

Somatic Embryogenesis and Plant Regeneration from Sugi (Japanese Cedar, Cryptomeria japonica D. Don, Cupressaceae) Seed Families by Marker Assisted Selection for the Male Sterility Allele ms1

by Tsuyoshi E. Maruyama, Saneyoshi Ueno, Satoko Hirayama, Takumi Kaneeda and Yoshinari Moriguchi

Plants 2020, 9(8), 1029; https://doi.org/10.3390/plants9081029 - 13 Aug 2020

Cited by 10 | Viewed by 3320

Abstract

One of the possible countermeasures for pollinosis caused by sugi (Cryptomeria japonica), a serious public health problem in Japan, is the use of male sterile plants (MSPs; pollen-free plants). However, the production efficiencies of MSPs raised by conventional methods are extremely [...] Read more.

One of the possible countermeasures for pollinosis caused by sugi (Cryptomeria japonica), a serious public health problem in Japan, is the use of male sterile plants (MSPs; pollen-free plants). However, the production efficiencies of MSPs raised by conventional methods are extremely poor, time consuming, and resulting in a high seedling cost. Here, we report the development of a novel technique for efficient production of MSPs, which combines marker-assisted selection (MAS) and somatic embryogenesis (SE). SE from four full sib seed families of sugi, carrying the male sterility gene MS1, was initiated using megagametophyte explants that originated from four seed collections taken at one-week intervals during the month of July 2017. Embryogenic cell lines (ECLs) were achieved in all families, with initiation rates varying from 0.6% to 59%. Somatic embryos were produced from genetic marker-selected male sterile ECLs on medium containing maltose, abscisic acid (ABA), polyethylene glycol (PEG), and activated charcoal (AC). Subsequently, high frequencies of germination and plant conversion (≥76%) were obtained on plant growth regulator-free medium. Regenerated plantlets were acclimatized successfully, and the initial growth of male sterile somatic plants was monitored in the field. Full article

(This article belongs to the Special Issue Advances in Plant Regeneration)

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14 pages, 2580 KiB

Open AccessArticle

tasiR-ARFs Production and Target Regulation during In Vitro Maize Plant Regeneration

by Brenda Anabel López-Ruiz, Vasti Thamara Juárez-González, Andrea Gómez-Felipe, Stefan De Folter and Tzvetanka D. Dinkova

Plants 2020, 9(7), 849; https://doi.org/10.3390/plants9070849 - 06 Jul 2020

Cited by 4 | Viewed by 3026

Abstract

During in vitro maize plant regeneration somatic cells change their normal fate and undergo restructuring to generate pluripotent cells able to originate new plants. Auxins are essential to achieve such plasticity. Their physiological effects are mediated by auxin response factors (ARFs) that bind [...] Read more.

During in vitro maize plant regeneration somatic cells change their normal fate and undergo restructuring to generate pluripotent cells able to originate new plants. Auxins are essential to achieve such plasticity. Their physiological effects are mediated by auxin response factors (ARFs) that bind auxin responsive elements within gene promoters. Small trans-acting (ta)-siRNAs, originated from miR390-guided TAS3 primary transcript cleavage, target ARF3/4 class (tasiR-ARFs). Here we found that TAS3b precursor as well as derived tasiR-ARFbD5 and tasiR-ARFbD6 display significantly lower levels in non-embryogenic callus (NEC), while TAS3g, miR390 and tasiR-ARFg are more abundant in the same tissue. However, Argonaute (AGO7) and leafbladeless 1 (LBLl) required for tasiR-ARF biogenesis showed significantly higher transcript levels in EC suggesting limited tasiR-ARF biogenesis in NEC. The five maize ARFs targeted by tasiR-ARFs were also significantly enriched in EC and accompanied by higher auxin accumulation with punctuate patterns in this tissue. At hormone half-reduction and photoperiod implementation, plant regeneration initiated from EC with transient TAS3g, miR390 and tasiR-ARFg increase. Upon complete hormone depletion, TAS3b became abundant and derived tasiR-ARFs gradually increased at further regeneration stages. ZmARF transcripts targeted by tasiR-ARFs, as well as AGO7 and LBL1 showed significantly lower levels during regeneration than in EC. These results indicate a dynamic tasiR-ARF mediated regulation throughout maize in vitro plant regeneration. Full article

(This article belongs to the Special Issue Advances in Plant Regeneration)

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Review

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25 pages, 747 KiB

Open AccessReview

Reinvigoration/Rejuvenation Induced through Micrografting of Tree Species: Signaling through Graft Union

by Isabel Vidoy-Mercado, Isabel Narváez, Elena Palomo-Ríos, Richard E. Litz, Araceli Barceló-Muñoz and Fernando Pliego-Alfaro

Plants 2021, 10(6), 1197; https://doi.org/10.3390/plants10061197 - 11 Jun 2021

Cited by 12 | Viewed by 4108

Abstract

Trees have a distinctive and generally long juvenile period during which vegetative growth rate is rapid and floral organs do not differentiate. Among trees, the juvenile period can range from 1 year to 15–20 years, although with some forest tree species, it can [...] Read more.

Trees have a distinctive and generally long juvenile period during which vegetative growth rate is rapid and floral organs do not differentiate. Among trees, the juvenile period can range from 1 year to 15–20 years, although with some forest tree species, it can be longer. Vegetative propagation of trees is usually much easier during the juvenile phase than with mature phase materials. Therefore, reversal of maturity is often necessary in order to obtain materials in which rooting ability has been restored. Micrografting has been developed for trees to address reinvigoration/rejuvenation of elite selections to facilitate vegetative propagation. Generally, shoots obtained after serial grafting have increased rooting competence and develop juvenile traits; in some cases, graft-derived shoots show enhanced in vitro proliferation. Recent advances in graft signaling have shown that several factors, e.g., plant hormones, proteins, and different types of RNA, could be responsible for changes in the scion. The focus of this review includes (1) a discussion of the differences between the juvenile and mature growth phases in trees, (2) successful restoration of juvenile traits through micrografting, and (3) the nature of the different signals passing through the graft union. Full article

(This article belongs to the Special Issue Advances in Plant Regeneration)

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28 pages, 1104 KiB

Open AccessReview

Natural Variation in Plant Pluripotency and Regeneration

by Robin Lardon and Danny Geelen

Plants 2020, 9(10), 1261; https://doi.org/10.3390/plants9101261 - 24 Sep 2020

Cited by 30 | Viewed by 7774

Abstract

Plant regeneration is essential for survival upon wounding and is, hence, considered to be a strong natural selective trait. The capacity of plant tissues to regenerate in vitro, however, varies substantially between and within species and depends on the applied incubation conditions. Insight [...] Read more.

Plant regeneration is essential for survival upon wounding and is, hence, considered to be a strong natural selective trait. The capacity of plant tissues to regenerate in vitro, however, varies substantially between and within species and depends on the applied incubation conditions. Insight into the genetic factors underlying this variation may help to improve numerous biotechnological applications that exploit in vitro regeneration. Here, we review the state of the art on the molecular framework of de novo shoot organogenesis from root explants in Arabidopsis, which is a complex process controlled by multiple quantitative trait loci of various effect sizes. Two types of factors are distinguished that contribute to natural regenerative variation: master regulators that are conserved in all experimental systems (e.g., WUSCHEL and related homeobox genes) and conditional regulators whose relative role depends on the explant and the incubation settings. We further elaborate on epigenetic variation and protocol variables that likely contribute to differential explant responsivity within species and conclude that in vitro shoot organogenesis occurs at the intersection between (epi) genetics, endogenous hormone levels, and environmental influences. Full article

(This article belongs to the Special Issue Advances in Plant Regeneration)

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19 pages, 1198 KiB

Open AccessEditor’s ChoiceReview

Advances in Plant Regeneration: Shake, Rattle and Roll

by Sergio Ibáñez, Elena Carneros, Pilar S. Testillano and José Manuel Pérez-Pérez

Plants 2020, 9(7), 897; https://doi.org/10.3390/plants9070897 - 16 Jul 2020

Cited by 28 | Viewed by 7464

Abstract

Some plant cells are able to rebuild new organs after tissue damage or in response to definite stress treatments and/or exogenous hormone applications. Whole plants can develop through de novo organogenesis or somatic embryogenesis. Recent findings have enlarged our understanding of the molecular [...] Read more.

Some plant cells are able to rebuild new organs after tissue damage or in response to definite stress treatments and/or exogenous hormone applications. Whole plants can develop through de novo organogenesis or somatic embryogenesis. Recent findings have enlarged our understanding of the molecular and cellular mechanisms required for tissue reprogramming during plant regeneration. Genetic analyses also suggest the key role of epigenetic regulation during de novo plant organogenesis. A deeper understanding of plant regeneration might help us to enhance tissue culture optimization, with multiple applications in plant micropropagation and green biotechnology. In this review, we will provide additional insights into the physiological and molecular framework of plant regeneration, including both direct and indirect de novo organ formation and somatic embryogenesis, and we will discuss the key role of intrinsic and extrinsic constraints for cell reprogramming during plant regeneration. Full article

(This article belongs to the Special Issue Advances in Plant Regeneration)

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20 pages, 891 KiB

Open AccessEditor’s ChoiceReview

Cellular, Molecular, and Physiological Aspects of In Vitro Plant Regeneration

by Siamak Shirani Bidabadi and S. Mohan Jain

Plants 2020, 9(6), 702; https://doi.org/10.3390/plants9060702 - 01 Jun 2020

Cited by 112 | Viewed by 15872

Abstract

Plants generally have the highest regenerative ability because they show a high degree of developmental plasticity. Although the basic principles of plant regeneration date back many years, understanding the cellular, molecular, and physiological mechanisms based on these principles is currently in progress. In [...] Read more.

Plants generally have the highest regenerative ability because they show a high degree of developmental plasticity. Although the basic principles of plant regeneration date back many years, understanding the cellular, molecular, and physiological mechanisms based on these principles is currently in progress. In addition to the significant effects of some factors such as medium components, phytohormones, explant type, and light on the regeneration ability of an explant, recent reports evidence the involvement of molecular signals in organogenesis and embryogenesis responses to explant wounding, induced plant cell death, and phytohormones interaction. However, some cellular behaviors such as the occurrence of somaclonal variations and abnormalities during the in vitro plant regeneration process may be associated with adverse effects on the efficacy of plant regeneration. A review of past studies suggests that, in some cases, regeneration in plants involves the reprogramming of distinct somatic cells, while in others, it is induced by the activation of relatively undifferentiated cells in somatic tissues. However, this review covers the most important factors involved in the process of plant regeneration and discusses the mechanisms by which plants monitor this process. Full article

(This article belongs to the Special Issue Advances in Plant Regeneration)

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