Functional Analysis of the Cotton Genome via Agrobacterium-Mediated VIGS Assay

Cotton is an important cash crop worldwide and serves as a significant source of fiber, feed, foodstuff, oil and biofuel products. Understanding the mechanisms of cotton gene functions and regulations will greatly facilitate us to genetically improve its traits with desired yield and enhanced resistance to biotic and abiotic stresses. However, its large size of complex genome, gene duplication, polyploidy, long growth cycle and laborious genetic transformation in limited varieties hinder us for high throughput functional genetic/genomic study in cotton. We have recently developed an Agrobacterium-mediated virus-induced gene silencing (VIGS) assay in several cotton cultivars. The genes of interest could be potently and readily silenced at the seedling stage with a consistently high efficiency. To monitor gene silencing efficiency, we have cloned cotton GrCla1 from G. raimondii, a homolog gene of Arabidopsis Cloroplastos alterados 1 (AtCla1) involved in chloroplast development. Silencing of GrCla1 results in albino phenotype on the newly emerging leaves, serving as a visual marker for silencing efficiency. We further established a cotton protoplast system to study gene functions by a gain-of-function approach. These technique advances made it possible to dissect the molecular and biochemical regulatory mechanisms of cotton genes under different biotic and abiotic stresses.