Cotton ovule culture: A tool for basic biology, biotechnology and cotton improvement

Abstract

Nearly 30 years ago the conditions for culturing immature cotton ovules were established to serve as a working research tool for investigating the physiology and biochemistry of fiber development. Not only has this tissue culture method been employed to characterize the biochemistry of plant cell expansion and secondary cell wall synthesis, but ovule cultures have contributed to numerous other aspects of plant cell physiology and development as well. In addition to basic studies on fiber development, cotton ovule cultures have been used to examine plant-fungal interactions, to model low temperature stress responses, to elucidate the pathways responsible for pigment formation in naturally pigmented fiber and to probe how cytoskeletal elements regulate cell wall organization. Success in rescuing Gossypium interspecific hybrids was dependent on ovule culture media formulations that could support early embryo development in ovulo. As tissues produced in culture are analyzed by increasingly more sophisticated techniques, there appear to be some differences between ovule growth in planta and ovule growth in vitro. Discerning how ovule culture fiber development is different from fiber development in field-grown plants can contribute valuable information for crop improvement. Cotton ovule cultures are an especially attractive model system for studying the effects of gravity on cell elongation, cellulose biosynthesis and embryo development and are excellent targets for examining transient expression of introduced gene constructs. With only minor modification, the procedure originally described by C. A. Beasley and I. P. Ting for growing cotton ovules in vitro will continue to be a useful research tool for the foreseeable future.

Cotton Fiber Growth in Planta and in Vitro. Models for Plant Cell Elongation and Cell Wall Biogenesis

“…In the last 30 years, cotton ovule cultures have been used by numerous investigators for a number of other applications (Triplett, 2000). Whether for analysis of suboptimal temperatures on cellulose biosynthesis (Haigler et al, 1991;Xie et al, 1993), looking at plant-fungal interactions (Mellon, 1986), or examining the structure and biochemistry of naturally pigmented cotton fibers (Ryser et al, 1983), cotton ovule cultures have proven to be a versatile research tool.…”

Nutrient and hormone levels in cotton ovules during embryony

“…Other major differences involve carbohydrate requirements, which are met in conventional plant tissue culture media primarily by sucrose, but in cotton ovules, glucose, fructose, arabinose and melibiose may also be important to embryony. Likewise, endogenous IAA levels in ovule fluid were 2-3 times higher than levels used in conventional cotton embryo culture media (Triplett 2000). Types and levels of cytokinins also differ with a mixture of cytokinins occurring with abrupt peaks in vivo but often only one cytokinin being used in vitro.…”

“…The extent to which this environment is responsible for normal embryo development is not fully understood. An approach for elucidating important interactions between embryos and maternal tissues is to chemically define tissues and fluids adjacent to embryos, from anthesis through embryo differentiation, and to conduct embryo culture experiments that simulate the chemical and physical parameters of ovules (Carman 1990(Carman , 1995Triplett 2000;Raghavan 2006). The nutrient and hormone content of fluids that nourish cotton (Gossypium hirsutum L.) embryos during development (ovule fluid) have not been reported.…”

Improving cotton embryo culture by simulating in ovulo nutrient and hormone levels

“…Using nurse tissues or solutions, a more or less normal embryony from zygotes or proembryos (embryos that have not yet formed cotyledonary and embryo axis meristems) has been achieved in vitro for (1) Gossypium hirsutum L. (cotton) through ovule culture (Stewart and Hsu 1977;Triplett 2000;Sacks 2008); (2) Zea mays L. (corn) by culturing zygotes and proembryos on various nurse tissues (Campenot et al 1992;Kranz and Lörz 1993;Mol et al 1993Mol et al , 1995Leduc et al 1996;Laurie et al 1999); (3) Triticum aestivum L. (wheat) by ovule culture or by culturing proembryos on nurse tissues (Comeau et al 1992;Kumlehn et al 1997); (4) Brassica juncea (L.) Czern. (mustard) by culturing proembryos in media containing coconut milk (Liu et al 1993); (5) Hordeum vulgare L. (barley) through ovule culture (Holm et al 1995); (6) Lolium multiflorum Lam.…”