Conifer Biology
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Maturation of somatic embryos in conifers: Morphogenesis, physiology, biochemistry, and molecular biology
IN VITRO CELLULAR & DEVELOPMENTAL BIOLOGY - PLANT
Volume 38, Number 2, 93-105 (2002), DOI: 10.1079/IVP2001262
Abstract
In the past 15 years tremendons progress has been made towards the development of systems for the induction and development of somatic embryos of coniferous species. Since the first report in 1985, several species have been induced to produce somatic embryos. This has been rendered possible by the development of rational media and improvement of culture conditions, which have resulted in increased embryo quality and higher conversion frequency. Understanding the physiological and biochemical events occurring during in vivo embryogenesis has been fundamental in the design of new protocols for improving the somatic embryogenic process. Specifically, the inclusions of abscisic acid (ABA) and osmotic agents, such as polyethylene glycol (PEG), have been shown to be necessary for the functional development of somatic embryos. In the past few years, physiological and biochemical investigations have been useful in increasing our knowledge on the mode of action of ABA and PEG during embryo development. In comparison with the flowering plants, our understanding on the molecular mechanisms regulating the embryogenic process in coniferous species is still very limited. The application of new molecular techniques is therefore fundamental towards this end. The emphasis of this review is on recent information dealing with the maturation of conifer somatic embryos.
Key words conifers - embryo maturation - abseisic acid - partial drying - polyethylene glycol
REVIEW PAPER
Embryogeny of gymnosperms: advances in synthetic seed technology of conifers
PLANT CELL, TISSUE AND ORGAN CULTURE
Volume 35, Number 1, 1-35 (1993), DOI: 10.1007/BF00043936
Abstract
Synthetic seed technology requires the inexpensive production of large numbers of high-quality somatic embryos. Proliferating embryogenic cultures from conifers consist of immature embryos, which undergo synchronous maturation in the presence of abscisic acid and elevated osmoticum. Improvements in conifer somatic embryo quality have been achieved by identifying the conditions in vitro that resemble the conditions during in ovulo development of zygotic embryos. One normal aspect of zygotic embryo development for conifers is maturation drying, which allows seeds to be stored and promotes normal germination. Conditions of culture are described that yield mature conifer somatic embryos that possess normal storage proteins and fatty acids and which survive either partial drying, or full drying to moisture contents similar to those achieved by mature dehydrated zygotic embryos. Large numbers of quiescent somatic embryos can be produced throughout the year and stored for germination in the spring, which simplifies production and provides plants of uniform size. This review focuses on recent advances in conifer somatic embryogenesis and synthetic seed technology, particularly in areas of embryo development, maturation drying, encapsulation and germination. Comparisons of conifer embryogeny are made with other gymnosperms and angiosperms.
Key words abscisic acid - angiosperm - cycad - osmotic stress - quiescence - seed evolution - somatic embryogenesis
C Stasolla, L Kong, EC Yeung… - … & Developmental Biology- …, 2002 - Springer
Page 1. MATURATION OF SOMATIC EMBRYOS IN CONIFERS: MORPHOGENESIS,
PHYSIOLOGY, BIOCHEMISTRY, AND MOLECULAR BIOLOGY CLAUDIO STASOLLA†,
LISHENG KONG‡, EDWARD C. YEUNG, AND TREVOR A. THORPE* ...
Cited by 59 - Related articles - BL Direct - All 5 versions
Claudio Stasolla, Lisheng Kong, Edward C. Yeung and Trevor A. Thorpe
Recent advances in conifer somatic embryogenesis: improving somatic embryo quality
PLANT CELL, TISSUE AND ORGAN CULTURE
Volume 74, Number 1, 15-35 (2003), DOI: 10.1023/A:1023345803336
Abstract
Somatic embryogenesis of coniferous species was first reported more than 20 years ago. Since then, there has been an explosion of research aimed at developing and optimizing protocols for efficient regeneration of plantlets. Although routinely used both as a means of propagation, as well as a valuable model system for investigating the structural, physiological, and molecular events occurring during embryo development,in vitro embryogenesis is still problematic for some coniferous species. Major problems include: low number of embryos generated; and low frequency of mature embryos able to convert into viable plantlets. Until recent years, despite the fact that embryogenesis is comprised of a sequence of defined steps which include proliferation of embryogenic tissue, embryo maturation, and germination, attempts at improving the whole procedure have been made almost exclusively during the maturation stage. This strategy was based on the assumption that successful regeneration is related to treatments provided during the development of the embryos. Major optimizations of the maturation medium have involved judicious selections of type and concentration of growth regulators, namely abscisic acid, and adjustments of the osmoticum of the culture medium. Extensive work has been conducted in defining the effects of plasmolysing and non-plasmolysing osmoticum agents during maturation, as well as in improving desiccation techniques required for the completion of the maturation program. In the last 2 years, however, work on spruce has clearly demonstrated that the early events in embryogenesis are crucial for the successful completion of the overall embryogenic program. The use of cell tracking techniques, implemented by physiological and molecular studies, has revealed that manipulations of the culture conditions early in the process can increase both number and quality of embryos produced in culture. Additional manipulations of the germination medium can also enhance germination and conversion frequency of somatic embryos matured in a sub-optimal environment. These new findings, together with the unraveling of molecular mechanisms involved in the control/regulation of embryo development hold considerable promise for clonal propagation in conifers.
apical meristems - conifer - conversion - embryo quality - germination - molecular biology - physiology - somatic embryogenesis
Cun-Xu Zhang, Qian Li and Lisheng Kong
ORIGINAL PAPER
Induction, development and maturation of somatic embryos in Bunge’s pine ( Pinus bungeana Zucc. ex Endl.)
PLANT CELL, TISSUE AND ORGAN CULTURE
Volume 91, Number 3, 273-280 (2007), DOI: 10.1007/s11240-007-9294-4
Abstract
Embryogenic tissue was induced from developing immature zygotic embryos in Bunge’s pine (Pinus bungeana Zucc. ex Endl.). Induction rate reached 84.4% with our best treatment. Zygotic embryos were dissected from megagametophytes and inoculated on different induction media, DCR1 (Gupta PK, Durzan DJ (1985) Plant Cell Rep 4:177–179), BM1 (Gupta PK, Pullman G (1991) U.S. Patent No. 5,036,00) and MSG (Becwar MR, et al. (1988) Somatic cell genetic of woody plants. Kluwer Academic Publishers, Dordrecht, pp. 1–18), supplemented with 2,4-dichlorophenoxyacetic acid (2, 4-D) and 6-benzylaminopurine (BA). DCR1was the best medium for initiating embryogenic tissue. Induction rates were affected significantly by developmental stages of explants. The highest induction rate was obtained with embryos collected on either June 20 or June 30 with 10 mg l−1 2, 4-D and 4 mg l−1 BA. Embryogenic tissue was subcultured monthly on DCR1 medium supplemented with 0.3 mg l−1 2, 4-D and 0.2 mg l−1 α-naphthaleneacetic acid. In order to enhance embryo maturation, embryogenic tissue was transferred onto DCR1 medium for two weeks, in which 1,000 mg l−1 myo-inositol was included and all plant growth regulators were eliminated. This pretreated tissue was then transferred onto a maturation medium that was DCR1 medium containing 50 g l−1 sucrose and 0.1 mg l−1 indolebutyric acid. In this study, benefits of embryo maturation were not observed when abscisic acid and polyethylene glycol were applied in the culture.
Keywords Bunge’s pine - Conifer - Pinus sp. - Somatic embryogenesis