[Cloning and functional analysis of chitinase gene GbCHI from sea-island cotton (Gossypium barbadense)].

Chitinase is one of the important pathogenesis-related (PR) proteins in plants. By comparative proteomics study, a novel pathogen-responsive chitinase (known as GbCHI) has been identified from sea-island cotton (Gossypium barbadense). The GbCHI cDNA was cloned from wilt-resistant sea-island cotton and the anti-fungal activity of the gene product was investigated. qRT-PCR analysis indicated that GbCHI was expressed constitutively in root, stem, leaf, flower, and ovule of cotton plant, and the expression could be induced by Verticillium dahliae and plant hormone SA, ACC, and JA. Subcellular localization analysis using GFP-tagged proteins showed that GbCHI-GFP fusion proteins were targeted mainly to the plasma membrane. Anti-fungal assay demonstrated that GbCHI could inhibit spore germination and hyphae growth of V. dahliae significantly. These results provide important information for understanding the cellular function of GbCHI and for exploring the application potential of this gene in molecular breeding of wilt-tolerant cotton plants.

[Changes in diversity of culturable microorganisms on leaf surface of transgenic Bt cotton].

In a field study, the quantitative changes of bacterial, actinomycetic and fungal populations on the leaf surface of transgenic Bt cotton (GK-12) and non-transgenic Bt cotton (Simian No. 3) were monitored at seedling, squaring, flowering and boll-opening stages, respectively, and the diversity of bacterial physiological groups was analyzed at flowering and boll-opening stages. The results showed that there was a positive correlation between the quantity of culturable microorganisms and the development of cotton. The total number of bacteria, fungi and actinomyces began to rise at seedling stage, reached its peak at flowering stage, and decreased markedly at boll-opening stage. The Simpson index, Shannon-Wiener index, and evenness index of bacterial physiological groups were higher at flowering stage, but lower at boll-opening stage on GK-12 than on Simian No. 3.