MOA Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan 430070, China.
Plant Physiol. 2024 May 31;195(2):1660-1680. doi: 10.1093/plphys/kiae130.
Low-temperature sensitivity at the germination stage is a challenge for direct seeding of rice in Asian countries. How Ca2+ and auxin (IAA) signaling regulate primary root growth under chilling remains unexplored. Here, we showed that OsCML16 interacted specifically with OsPILS7a to improve primary root elongation of early rice seedlings under chilling. OsCML16, a subgroup 6c member of the OsCML family, interacted with multiple cytosolic loop regions of OsPILS7a in a Ca2+-dependent manner. OsPILS7a localized to the endoplasmic reticulum membranes and functioned as an auxin efflux carrier in a yeast growth assay. Transgenics showed that presence of OsCML16 enhanced primary root elongation under chilling, whereas the ospils7a knockout mutant lines showed the opposite phenotype. Moreover, under chilling conditions, OsCML16 and OsPILS7a-mediated Ca2+ and IAA signaling and regulated the transcription of IAA signaling-associated genes (OsIAA11, OsIAA23, and OsARF16) and cell division marker genes (OsRAN1, OsRAN2, and OsLTG1) in primary roots. These results show that OsCML16 and OsPILS7a cooperatively regulate primary root elongation of early rice seedlings under chilling. These findings enhance our understanding of the crosstalk between Ca2+ and IAA signaling and reveal insights into the mechanisms underlying cold-stress response during rice germination.
低温敏感性在发芽阶段是亚洲国家直接播种水稻的一个挑战。钙（Ca2+）和生长素（IAA）信号如何调节冷胁迫下主根的生长仍不清楚。在这里，我们表明 OsCML16 与 OsPILS7a 特异性相互作用，以改善冷胁迫下早期水稻幼苗的主根伸长。OsCML16 是 OsCML 家族的 6c 亚组成员，以 Ca2+依赖的方式与 OsPILS7a 的多个细胞质环区相互作用。OsPILS7a 定位于内质网膜，并在酵母生长测定中作为生长素外排载体发挥作用。转基因显示，OsCML16 的存在增强了冷胁迫下的主根伸长，而 ospils7a 敲除突变体系则表现出相反的表型。此外，在冷胁迫条件下，OsCML16 和 OsPILS7a 介导的 Ca2+和 IAA 信号转导，并调节 IAA 信号转导相关基因（OsIAA11、OsIAA23 和 OsARF16）和细胞分裂标记基因（OsRAN1、OsRAN2 和 OsLTG1）的转录。这些结果表明，OsCML16 和 OsPILS7a 协同调节冷胁迫下早期水稻幼苗的主根伸长。这些发现增强了我们对 Ca2+和 IAA 信号转导之间串扰的理解，并揭示了在水稻发芽过程中冷胁迫响应的机制。
