Lulu Bi1,2, Lin Weng1, Zhuyan Jiang1,2, Han Xiao3. 1. National Key Laboratory of Plant Molecular Genetics, CAS Center for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, 300 Fenglin Rd, Shanghai, 200032, China. 2. University of the Chinese Academy of Sciences, No. 19A Yuquanlu, Beijing, 100049, China. 3. National Key Laboratory of Plant Molecular Genetics, CAS Center for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, 300 Fenglin Rd, Shanghai, 200032, China. hanxiao@sibs.ac.cn.
Abstract
MAIN CONCLUSION: Gene expression and functional analysis of the tomato IQD gene SUN24 revealed that it regulates seed germination through ABA signaling pathway. Ca2+ signaling plays crucial roles in diverse biological processes including ABA-mediated seed germination. The plant-specific IQ67-Domain (IQD) proteins are hypothesized to regulate Ca2+ signaling and plant development through interactions with calmodulins (CaMs). Despite a few IQD genes have been identified to regulate herbivore resistance and plant growth and development, the molecular functions of most members in this gene family are not known. In this study, we characterized the role of the tomato IQD gene SUN24 in seed germination. Using pSUN24::GUS reporter lines and by quantitative reverse transcription PCR analysis, we show that SUN24 is mainly expressed in the roots, flowers, young fruits, seeds, and other young developing tissues, and its expression is repressed by ABA treatments. Functional analysis shows that knockdown of SUN24 expression by RNA interference delays seed germination, whereas overexpression of this IQD gene promotes germination. Further gene expression analysis reveals that SUN24 negatively regulates expression of two key ABA signaling genes Solanum lycopersicum ABA-insensitive 3 (SlABI3) and SlABI5 in germinating seeds. Moreover, SUN24, targeting to microtubule and nuclear bodies, can interact with four tomato CaMs (SlCaM1, 2, 3, and 6) in yeast cells. Our results demonstrate that SUN24 regulates seed germination through ABA signaling pathway, expanding our understanding of the roles of the IQD protein family members in plant physiological processes.
MAIN CONCLUSION: Gene expression and functional analysis of the tomato IQD gene SUN24 revealed that it regulates seed germination through ABA signaling pathway. Ca2+ signaling plays crucial roles in diverse biological processes including ABA-mediated seed germination. The plant-specific IQ67-Domain (IQD) proteins are hypothesized to regulate Ca2+ signaling and plant development through interactions with calmodulins (CaMs). Despite a few IQD genes have been identified to regulate herbivore resistance and plant growth and development, the molecular functions of most members in this gene family are not known. In this study, we characterized the role of the tomato IQD gene SUN24 in seed germination. Using pSUN24::GUS reporter lines and by quantitative reverse transcription PCR analysis, we show that SUN24 is mainly expressed in the roots, flowers, young fruits, seeds, and other young developing tissues, and its expression is repressed by ABA treatments. Functional analysis shows that knockdown of SUN24 expression by RNA interference delays seed germination, whereas overexpression of this IQD gene promotes germination. Further gene expression analysis reveals that SUN24 negatively regulates expression of two key ABA signaling genes Solanum lycopersicum ABA-insensitive 3 (SlABI3) and SlABI5 in germinating seeds. Moreover, SUN24, targeting to microtubule and nuclear bodies, can interact with four tomato CaMs (SlCaM1, 2, 3, and 6) in yeast cells. Our results demonstrate that SUN24 regulates seed germination through ABA signaling pathway, expanding our understanding of the roles of the IQD protein family members in plant physiological processes.