Cultures of Gossypium barbadense cotton ovules offer insights into the microtubule-mediated control of fiber cell expansion.

MAIN CONCLUSION: A novel method for culturing ovules of Gossypium barbadense allowed in vitro comparisons with Gossypium hirsutum and revealed variable roles of microtubules in controlling cotton fiber cell expansion. Cotton fibers undergo extensive elongation and secondary wall thickening as they develop into our most important renewable textile material. These single cells elongate at the apex as well as elongating and expanding in diameter behind the apex. These multiple growth modes represent an interesting difference compared to classical tip-growing cells that needs to be explored further. In vitro ovule culture enables experimental analysis of the controls of cotton fiber development in commonly grown Gossypium hirsutum cotton, but, previously, there was no equivalent system for G. barbadense, which produces higher quality cotton fiber. Here, we describe: (a) how to culture the ovules of G. barbadense successfully, and (b) the results of an in vitro experiment comparing the role of microtubules in controlling cell expansion in different zones near the apex of three types of cotton fiber tips. Adding the common herbicide fluridone, 1-Methyl-3-phenyl-5-[3-(trifluoromethyl)phenyl]-4(1H)-pyridinone, to the medium supported G. barbadense ovule culture, with positive impacts on the number of useful ovules and fiber length. The effect is potentially mediated through inhibited synthesis of abscisic acid, which antagonized the positive effects of fluridone. Fiber development was perturbed by adding colchicine, a microtubule antagonist, to ovules of G. barbadense and G. hirsutum cultured 2 days after flowering. The results supported the zonal control of cell expansion in one type of G. hirsutum fiber tip and highlighted differences in the role of microtubules in modulating cell expansion between three types of cotton fiber tips.

Cotton fiber tips have diverse morphologies and show evidence of apical cell wall synthesis.

Cotton fibers arise through highly anisotropic expansion of a single seed epidermal cell. We obtained evidence that apical cell wall synthesis occurs through examining the tips of young elongating Gossypium hirsutum (Gh) and G. barbadense (Gb) fibers. We characterized two tip types in Gh fiber (hemisphere and tapered), each with distinct apical diameter, central vacuole location, and distribution of cell wall components. The apex of Gh hemisphere tips was enriched in homogalacturonan epitopes, including a relatively high methyl-esterified form associated with cell wall pliability. Other wall components increased behind the apex including cellulose and the α-Fuc-(1,2)-ß-Gal epitope predominantly found in xyloglucan. Gb fibers had only one narrow tip type featuring characters found in each Gh tip type. Pulse-labeling of cell wall glucans indicated wall synthesis at the apex of both Gh tip types and in distal zones. Living Gh hemisphere and Gb tips ruptured preferentially at the apex upon treatment with wall degrading enzymes, consistent with newly synthesized wall at the apex. Gh tapered tips ruptured either at the apex or distantly. Overall, the results reveal diverse cotton fiber tip morphologies and support primary wall synthesis occurring at the apex and discrete distal regions of the tip.

Cotton fiber: a powerful single-cell model for cell wall and cellulose research.

Cotton fibers are single-celled extensions of the seed epidermis. They can be isolated in pure form as they undergo staged differentiation including primary cell wall synthesis during elongation and nearly pure cellulose synthesis during secondary wall thickening. This combination of features supports clear interpretation of data about cell walls and cellulose synthesis in the context of high throughput modern experimental technologies. Prior contributions of cotton fiber to building fundamental knowledge about cell walls will be summarized and the dynamic changes in cell wall polymers throughout cotton fiber differentiation will be described. Recent successes in using stable cotton transformation to alter cotton fiber cell wall properties as well as cotton fiber quality will be discussed. Futurec prospects to perform experiments more rapidly through altering cotton fiberwall properties via virus-induced gene silencing will be evaluated.

Analysis of CoQ10 in cultivated tobacco by a high-performance liquid chromatography-ultraviolet method.

Coenzyme Q (CoQ) is a naturally occurring lipid-soluble quinone that performs multiple functions in all living cells and has become a popular antioxidant supplement, a coadjuvant in the treatment of heart disease, and the object of study for treating neurodegenerative disorders. Although there are many tools for CoQ analysis of microbial and animal samples, there have been relatively few reports of methods for CoQ analysis of green plants. This work describes a method for the routine analysis of coenzyme Q(10) in green leaf tissue of cultivated Nicotiana tabacum (tobacco) using high-performance liquid chromatography (HPLC) with UV detection. The method was applied to the analysis of CoQ(10) in N. tabacum 'KY14' leaves at different stalk positions representing young lanceolate to senescing leaves, and it was found that CoQ(10) increased as leaf position changed down the stalk from 18.69 to 82.68 µg/g fw. The method was also used to observe CoQ(10) in N. tabacum 'NC55' and N. tabacum 'TN90LC' leaves over time, finding that CoQ(10) leaf content remained relatively stable from 3 to 6 weeks but increased in both cultivars at 8 weeks. This method will likely be useful in the analysis of CoQ(10) in the green leaves of other plant species.