Pepper heat shock transcription factor A1d contributes to seed thermotolerance and germination vigor

Abstract

Pepper (Capsicum annuum L.) is an important economic vegetable and have a high value in the medicinal, chemical additive and other industries. However, heat stress during seed germination and the loss of seed vigor during seed conservation affect the seed germination, development, yield, and economic value of pepper. To fulfill the demands of industries, it is crucial to explore the potential molecular mechanism of pepper seed thermotolerance and vigor for developing good quality pepper seeds. In the present study, we found that pepper CaHsfA1d gene is highly expressed in seed development, and its expression decreased with entering the germination state. Heat induced a declined expression of CaHsfA1d gene during seed germination. However, overexpression of CaHsfA1d in Arabidopsis significantly improved seed thermotolerance, and enhanced the transcript levels of thermotolerant (AtHsfA2 and AtHsp18.2) and antioxidative (AtGSTU5) genes during seeds germination after heat stress. In addition, CaHsfA1d transgenic Arabidopsis seeds showed enhanced resistance to accelerated aging and signifying their possible role in seed germination vigor. Research on seed germination under environmental stresses and seed vigor are new topics in pepper seed science, and our study provides a reference for further studying the mechanism of pepper seed defense and crop resistance breeding.