Temporal expression of floral proteins interacting with CArG1 region of CsAP3 gene in Crocus sativus L.

Abstract

Crocus sativus L. (Saffron), a monocot triploid species belonging to the Iridaceae family, is also called golden crop owing to its precious stigmas enriched with flavanoids Crocin, Picocrocin and Safranal. Unlike majority of plants which follow typical ABC model of floral development, deviations from ABC model have been reported in Saffron flowers which could probably be implicated in growth and development of distinct Saffron stigmas. CsAP3 is a critical gene regulating stigma development in Saffron. Its promoter consists of three CArG regions which play pivotal role in the expression of AP3 gene, of which CArG1 is the binding site for activator proteins thus regulating floral growth. Keeping in view the growth regulating characteristics of CArG1, we choose to identify the nuclear factors binding to this region in Saffron. Purified nuclear proteins were allowed to bind synthetic CArG1 sequence and the complex was subjected to protein identification using LCMS. Out of the 5 major protein hits in LCMS, NAC-like protein (NAP) was identified as a conspicuous homeotic protein interacting with CArG1 region of AP3 promoter. Gene expression analysis of CsAP3 and CsNAP at different stages of flower development showed stage-specific expression of both the genes however, no direct correlation between CsAP3 and CsNAP gene expression could be observed, even though both these genes are present in the same pathway and expressed at same time. It is possible that CsNAP may be regulating CsAP3 expression via some other mediators, indirectly which needs further molecular profiling.