TCS as a reporter system to study CKs in cotton

Germplasm and Genetic Stocks

poster

Zeng, Jian-Yan; Zhang, Mi; Bai, Wen-Qin; Pei, Yan

Zeng, Jian-Yan

Pei, Yan

Plant type is a key factor that influences planting density, fruiting and harvest. Cytokinins (CKs) are plant hormone regulating cell division, and play an important role in organogenesis. To investigate the dynamic change of endogenous CKs in cotton plant and its effect on morphogenesis of cotton, a synthetic cytokinin-inducible promoter TCS fused with GUS reporter gene was introduced into upland cotton through agrobacterium-mediated transformation. qPCR analysis showed that only CKs could induce expression of GUS gene, and the expression level was increased with the enhancement of CKs. Histochemical staining showed that GUS activity was strongly detected in shoots meristem and vascular tissue of stems and leaves. In flower buds, GUS signal mainly appeared in floral primordium of early stage when floral organs, including bracts, calyxes, stamens and carpels, began differentiation. The distribution of CKs was further confirmed by in situ immuno-hybridization using antibodys against ZR and iPR, respectively. Then, we used TCS::GUS cotton to analyze interaction of IAA and CKs in fruiting stems. Shoots of fruiting branches were decapitated and detected the distribution of CKs in the decapitated stems. The decapitation led to a considerable increase of GUS signal. LC-MS determination showed that the decapitation of fruiting stems resulted in a significant decrease of IAA, while a noticeable increase of CKs in the stem. Meanwhile, the expression of the key cytokinin biosynthesis genes (GhIPTs) was significantly up-regulated. In addition, application of IAA to the apexes of decapitated stems could counter the effect of decapitation. These results suggested that decapitation leads to a decrease of IAA, which in turn up-regulates the expressions of GhIPTs. Taken together, TCS::GUS is convenient for monitoring the change of endogenous CKs and studying the role of CKs in cotton. Key words: cotton; cytokinins; TCS promoter This work was supported by NSFC (31130039 and 31201248) and NSF of Chongqing (cstc2012jjjq0011)