Secretory lipid transfer protein OsLTPL94 acts as a target of EAT1 and is required for rice pollen wall development

Yang Tao, Ting Zou, Xu Zhang, Rui Liu, Hao Chen, Guoqiang Yuan, Dan Zhou, Pingping Xiong, Zhiyuan He, Gongwen Li, Menglin Zhou, Sijing Liu, Qiming Deng, Shiquan Wang, Jun Zhu, Yueyang Liang, Xiumei Yu, Aiping Zheng, Aijun Wang, Huainian Liu, Lingxia Wang, Ping Li*, Shuangcheng Li*

The Plant Journal（IF=6.417，TOP），2021

https://onlinelibrary.wiley.com/doi/10.1111/tpj.15443

Summary

Plant pollen wall protects the male gametophyte from various biotic and abiotic stresses. The formation of a unique pollen wall structure and elaborate exine pattern is a well-organized process, which needs coordination between reproductive cells and the neighboring somatic cells. However, molecular mechanisms underlying this process remain largely unknown. Here, we report a rice male-sterile mutant (l94) exhibited defective pollen exine patterning and abnormal tapetal cell development. MutMap and knock-out analyses demonstrated that the causal gene encodes a type-G non-specific lipid transfer protein (OsLTPL94). Histological and cellular analyses established that OsLTPL94 is strongly expressed in the developing microspores and tapetal cells, and its protein is secreted to the plasma membrane. The l94 mutation impeded the secretory ability of OsLTPL94 protein. Further in vivo and in vitro investigations supported that ETERNAL TAPETUM 1 (EAT1), a basic helix-loop-helix transcription factor (bHLH TF), activated OsLTPL94 expression through direct binding to the E-box motif of OsLTPL94 promoter, which was supported by the positive correlation between the expression of EAT1 and OsLTPL94 in two independent eat1 mutants. Our findings suggest that the secretory OsLTPL94 plays a key role in the coordinated development of tapetum and microspores with the regulation of EAT1.