Jane K. Dever

Cotton GhBAK1 mediates Verticillium wilt resistance and cell death.

Virus-induced gene silencing (VIGS) offers a powerful approach for functional analysis of individual genes by knocking down their expression. We have adopted this approach to dissect gene functions in cotton resistant to Verticillium wilt, one of the most devastating diseases worldwide. We showed here that highly efficient VIGS was obtained in a cotton breeding line (CA4002) with partial resistance to Verticillium wilt, and GhMKK2 and GhVe1 are required for its resistance to Verticillium wilt. Arabidopsis AtBAK1/SERK3, a central regulator in plant disease resistance, belongs to a subfamily of somatic embryogenesis receptor kinases (SERKs) with five members, AtSERK1 to AtSERK5. Two BAK1 orthologs and one SERK1 ortholog were identified in the cotton genome. Importantly, GhBAK1 is required for CA4002 resistance to Verticillium wilt. Surprisingly, silencing of GhBAK1 is sufficient to trigger cell death accompanied with production of reactive oxygen species in cotton. This result is distinct from Arabidopsis in which AtBAK1 and AtSERK4 play redundant functions in cell death control. Apparently, cotton has only evolved SERK1 and BAK1 whereas AtSERK4/5 are newly evolved genes in Arabidopsis. Our studies indicate the functional importance of BAK1 in Verticillium wilt resistance and suggest the dynamic evolution of SERK family members in different plant species.

Simple and Effective Method for Evaluating Cotton Seedlings for Resistance to Thrips in a Greenhouse, and a Thrips Species Composition on the Texas High Plains

Abstract. The method described in this paper uses wheat, Triticum aestivum L., grown in a greenhouse as the rearing medium for thrips forced to move to cotton, Gossypium hirsutum L., seedlings after the wheat was killed with herbicide. As measured by numbers of thrips and reduction of leaf surface area, the method produced abundant thrips pressure and was useful for initial evaluation of cotton for resistance. The method was used to evaluate cotton seedlings for six years and had a 0% failure rate. Western flower thrips, Frankliniella occidentalis Pergande, followed by onion thrips, Thrips tabaci Lindeman, were dominant during the study. Numbers of thrips of other species were scarce.

The U.S. National Cotton Germplasm Collection – Its Contents, Preservation, Characterization, and Evaluation

The early history of the cotton industry in the U.S. was, for the most part, a story of importation and adaptation of cottons from Mexico, Guatemala, and the tropics of the Western Hemi‐ sphere. By the 19th century there were two distinctive types of upland cotton, with distinctive origins, being grown in the U.S. One type, known as green-seeded cotton, was from southern Mexico. The other dominant type of upland, white-seeded cotton, had its origins in the central plateau of Mexico [1,2]. Although these cottons were grown extensively, no coordinated efforts were made to maintain the original stocks or their progeny. Modern, systematic collection and preservation of cotton in the U.S. only began in response to the outbreak of the boll weevil in the 1880’s [3]. Three collection trips between 1902 and 1906 were responsible for the introduc‐ tion of two cottons, Acala and Kekchi, which would contribute significantly to the develop‐ ment of modern U.S. cultivars [4]. From these initial collecting trips and ensuing trips, federal, university and state experiment stations began to assemble the germplasm collections. Also from these efforts there sprang collaborative efforts that were formalized into U.S. regional projects involving scientists and members from all aspects of the U.S. cotton industry. The first Regional Research Project was S-1 in 1950 (succeeded by many) and it established a priority of acquiring and studying diverse germplasm for cotton improvement [5-7]. Increased organization and centralization of germplasm activities was necessary to manage and increase

Characterization of transgenic cotton ( Gossypium hirsutum L.) over-expressing Arabidopsis thaliana Related to ABA-insensitive3(ABI3)/Vivparous1 (AtRAV1) and AtABI5 transcription factors: improved water use efficiency through altered guard cell physiology

We investigated select transgenic lines of Gossypium hirsutum that over-express AtRAV1 or AtABI5 transcription factors. The hypothesis is that these lines have enhanced responses to abscisic acid (ABA) resulting in greater water use efficiencies (WUE). We measured leaf surface temperatures (LST), stomatal density, absolute and relative sizes of guard cell apertures, and ABA concentrations in cotyledons. We characterized transgene protein expression and activities in transient assays in Nicotiana benthamiana, in transgenic cotton seeds by immunoblot and by endogenous expression in leaves of an effector of ABA responses (GhDREB). AtRAV11-1-5 and AtABI51-1-1 over-expression lines had trends of lower levels of ABA in well-watered and drought-stressed cotyledons, and all events tested had higher leaf stomatal conductance and photosynthesis rates under drought in greenhouse, and lower LSTs than control Coker 312 under drought stress conditions. Notably, AtRAV11-1-5 cotyledons had significantly higher stomatal densities and 26% smaller guard cell apertures than Coker 312 under drought stress, providing a plausible explanation why LSTs across lines were lower concordant with smaller stomatal apertures. These traits may contribute to intrinsic WUE and assimilate traits of larger leaf areas and longer boll fibers previously shown in these and several independent AtRAV1 and AtABI5 events in the greenhouse and field. These results are consistent with the hypothesis that over-expression of AtRAV1 results in an ABA-hypersensitive phenotype manifest as reduced expression of endogenous GhDREB effector, and lower levels of endogenous ABA in cotyledons associated with greater reductions in pore apertures during stress and increased stomatal density.