1a. Objectives (from AD-416):
1. Quantitatively evaluate molecular, biochemical, and structural changes of fiber tissues in cotton plants grown in the field under well-watered, deficit irrigation, and dryland conditions. 2. Evaluate the impacts of different levels of drought stress on fiber quality and lint and seed yields, and analyze the relation of fiber quality traits with those changes detected in objective 1.
1b. Approach (from AD-416):
Transgenic cotton lines harboring CesA1-GUS reporter gene construct will be planted in the research field of USDA-ARS-CSRL at Lubbock, Texas. Two irrigation levels controlled by underground dripping irrigation systems will be applied to study the effect of drought stress on fiber development and fiber quality traits. To determine when and how much of the GUS gene is expressed in cotton fiber cell, total RNA in each of the harvested fiber tissues will be isolated and quantitative RT-PCR will be performed. The results will reveal the dynamic changes of GUS gene and gene product in fiber tissues of cotton plants grown under different irrigation levels throughout the sampling period (10, 14, 17, 19, 21, 24, and 27 dpa). At the same time, the structural and cell wall composition changes in fiber over the sampling time will be analyzed using FTIR and TGA technology at FBRI-TTU. Thirty FTIR spectra per sample will be acquired for each developmental stage. The correlation between structural and composition changes and molecular and biochemical changes (mentioned above) in fiber will be analyzed firstly for cotton plants grown under each irrigation level. Second, the association of dynamic changes of these traits with different levels of drought stress will be analyzed. The difference in these dynamic changes between drought-stressed and well-watered cotton plants will indicate the effects of drought stress on fiber development during secondary cell wall deposition and maturation processes. The correlation of drought stress with traits related to fiber quality and yield will be analyzed statistically. and cotton fiber quality and yield triats that are being mostly affected by field drought stress will be identified.
3. Progress Report:
In 2012, four CesA1-GUS transgenic cotton lines were planted for the second year, with three different irrigation levels (well-watered, deficit irrigation 33%, and dryland cotton) at USDA-ARS-CSRL location in Lubbock, Texas, with three replicates per condition. We have started to tag cotton flowers daily as they open. Cotton bolls at set DPA will be harvested, and fiber tissues harvested. GUS reporter gene activities in fiber tissues will be quantitatively determined by fluorometric analysis. The pattern of CesA1 gene expression during secondary cell wall deposition phase of fiber development will be examined. The cooperator's lab at FBRI-TTU will conduct fiber structural analysis using FTIR technology and microscopic cross-section images analysis. Results obtained in both labs will be analyzed statistically.