OsCNGC13 promotes seed-setting rate by facilitating pollen tube growth in stylar tissues.

Yongsheng Xu ,Haiyang Wang,Yang Yu,Yulong Ren,Ying Wang,Xin Zhang,Yunlong Wang,Yu Long,Ling Jiang,Jiachang Wang,Shanshan Zhu,Fuqing Wu,Jie Yang,Chuanyin Wu,Yihua Wang,Huan Zhang,Xiuping Guo,Jun Chen,Qian Lin

doi:10.1371/journal.pgen.1006906

Abstract

Seed-setting rate is a critical determinant of grain yield in rice (Oryza sativa L.). Rapid and healthy pollen tube growth in the style is required for high seed-setting rate. The molecular mechanisms governing this process remain largely unknown. In this study, we isolate a dominant low seed-setting rate rice mutant, sss1-D. Cellular examination results show that pollen tube growth is blocked in about half of the mutant styles. Molecular cloning and functional assays reveals that SSS1-D encodes OsCNGC13, a member of the cyclic nucleotide-gated channel family. OsCNGC13 is preferentially expressed in the pistils and its expression is dramatically reduced in the heterozygous plant, suggesting a haploinsufficiency nature for the dominant mutant phenotype. We show that OsCNGC13 is permeable to Ca2+. Consistent with this, accumulation of cytoplasmic calcium concentration ([Ca2+]cyt) is defective in the sss1-D mutant style after pollination. Further, the sss1-D mutant has altered extracellular matrix (ECM) components and delayed cell death in the style transmission tract (STT). Based on these results, we propose that OsCNGC13 acts as a novel maternal sporophytic factor required for stylar [Ca2+]cyt accumulation, ECM components modification and STT cell death, thus facilitating the penetration of pollen tube in the style for successful double fertilization and seed-setting in rice.

Highlights

Rice (Oryza sativa L.) is the staple food for more than half of the world’s population, and a model species for plant developmental and genetic studies [1]
Our results suggest that OsCNGC13 acts as a novel maternal sporophytic factor required for stylar [Ca2+]cyt accumulation, extracellular matrix components modification and style cell death, facilitating the penetration of pollen tube in the style for successful double fertilization and seedsetting in rice
These findings provide new insights into the molecular genetic control mechanisms of seed-setting rate/grain yield in rice and expand our knowledge on the cyclic nucleotide-gated channel proteins in plant sexual reproduction

Summary

Introduction

Rice (Oryza sativa L.) is the staple food for more than half of the world’s population, and a model species for plant developmental and genetic studies [1]. Grain number per panicle, grain weight and seed-setting rate constitute the major determinants of grain yield in rice [2]. Increasing effort has been made to elucidate the genetic control of seed-setting rate in rice as low seed-setting rate of Indica-Japonica hybrid has become a bottleneck limiting further improvement of hybrid grain yield [3]. Low seed-setting rate in rice could result from spikelet sterility due to abnormal floret structures, defective pollen grain or embryo sac development, impaired anther dehiscence, gametophytic incompatibility or inappropriate temperature at the reproductive stage. Pollen semi-sterility encodes a kinesin-1-like protein important for male meiosis, anther dehiscence, and fertility in rice [4]. Our understanding of the genetic control of seedsetting rate in rice still remains very fragmented

Methods

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Discussion

Conclusion