Project Summaries

11-816TX  Project Manager: D. C. Jones

ANALYZING THE EFFECT OF DROUGHT STRESS ON TRAITS CONTRIBUTING TO COTTON FIBER QUALITY

Junping Chen, USDA-ARS

Drought is a major environmental stress that reduces cotton yield and fiber quality.  Due to the inherent difficulties of studying fiber tissue and the lack of markers to monitor the fiber development, little is known about the molecular processes that are critical to the formation of high quality fiber and the association of these processes with drought tolerance in cotton (their performance under drought).  In 2011-2012, we studied the impacts of drought on fiber development and fiber quality traits, using transgenic cotton plants harboring a cellulose synthase A1 (CesA1) genepromoter and a GUS reporter construct. CesA1 is a critical gene for fiber secondary cell wall development. This promoter-reporter system allows us to monitor molecular changes inside fiber cell during fiber development. The Fourier Transform Infrared spectroscopy and other instruments were employed to examine structural changes of fiber cell during secondary cell wall synthesis. Fiber quality traits of mature fibers were analyzed by HIV and AFIS. The goal of this project is to identify processes that are most sensitive to drought stress and critical for fiber quality traits. The knowledge gained from this study can aid the development of rational approaches to improve fiber quality under drought.

Three levels of field drought stress experiments were performed in 2011 and 2012: Four CesA1-GUS reporter transgenic cotton lines along with wild-type control were planted in well-watered, deficit irrigation 33%, and dryland field in 2011 and 2012. Cotton flowers were tagged daily on the day of flowering. Bolls were harvested at set DPAs (10-56) and fiber tissues were collected and processed for various analyses. Fiber materials of 2010-2012 field studies (3 years) were analyzed for CesA1 gene activities (GUS assay) and those of 2010-2011 field study (2 years) were analyzed for structural and compositional changes of fiber cells.

Drought stress shifted the timing and shortened the duration of cellulose production in fiber tissues and caused cotton fibers to enter maturation phase much early: The results from reporter gene GUS activity analysis showed that cellulose production in fibers of drought stressed plants starts, peaks, and ends much earlier than in those of well-watered plants. As a result, the phases of fiber cell elongation and secondary cell wall synthesis were shortened for cottons under drought stress. Results from fiber structural and composition analyses showed that fibers of drought stressed plants matured much faster than those of well-watered plants. The drought caused changes in cellulose production in fiber tissues which are tightly correlated with the changes in the speed of secondary cell wall deposition and maturity of fiber cells under drought.

Drought stress caused reduction in fiber yield and fiber quality.  Fiber analysis results show drought stress significantly reduced fiber length, fiber elongation and fiber strength. Fibers produced under drought had more immature fibers and were less uniform than those produced under well-watered condition. The impact of drought on micronaire and fineness were less apparent.  Drought stress also caused significant reduction in plant size, boll numbers and substantial yield loss.

The results of this study indicate that cellulose production in fiber tissues is very sensitive to drought stress. The timing, amount, and duration of cellulose production during secondary cell wall synthesis of fiber cells are closely associated with fiber quality traits such as elongation, length, maturity, and  uniformity. Molecular modification of regulatory processes for cellulose production of cotton fibers in response to drought stress could lead to the improvement of fiber quality traits for cotton plants grown under dryland and/or drought stressed conditions.

 

Project Year: 2012
 

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