Silencing of Hindered Flowering and Boll Cracking in Upland Cotton

The opening of cotton bolls is an important characteristic that influences the precocity of cotton. In the field, farmers often use chemical defoliants to induce cotton leaves to fall off earlier, thus accelerating the cracking of cotton bolls. However, the molecular mechanism of cotton boll cracking remains unclear. We identified ten subfamily genes in upland cotton. Three pairs of AG subfamily genes () were amplified via tandem duplication. The promoters of the contained a diverse array of -acting regulatory elements related to light responses, abiotic stress, phytohormones and plant growth and development. Transcriptomic analyses revealed that the expression levels of subfamily genes were lower in vegetative tissues than in flower and fruit reproductive organs. The qRT-PCR results for different tissues revealed that the transcript level was highest in the cotton boll shell, and was selected as the target gene after comprehensive analysis. We further investigated the functional role of using virus-induced gene silencing (VIGS). Compared with those of the control plants, the flowering and boll cracking times of the -silenced plants were significantly delayed. Moreover, the results of paraffin sectioning at the back suture line of the cotton bolls revealed that the development of the dehiscence zone (DZ) occurred later in the -silenced plants than in the control plants. Furthermore, at the same developmental stage, the degree of lignification in the silenced plants was lower than that in the plants transformed with empty vector. The expression of several upland cotton genes homologous to key pod cracking genes was significantly downregulated in the -silenced plants. These results revealed that silencing delayed the flowering and cracking of cotton bolls and that the cracking of cotton bolls was delayed due to effects on DZ development. These findings are highly important for future studies of the molecular mechanism of cotton boll cracking and for breeding early-maturing and high-quality cotton varieties.