Rice Calcineurin B-Like Protein-Interacting Protein Kinase 31 (OsCIPK31) Is Involved in the Development of Panicle Apical Spikelets

Abstract

Panicle apical abortion (PAA) causes severe yield losses in rice production, but details about its development and molecular basis remain elusive. Herein, a PAA mutant, <i>paa1019</i>, was identified among the progeny of an elite indica maintainer rice line Yixiang 1B (YXB) mutagenized population obtained using ethyl methyl sulfonate. The abortion rate of spikelets in <i>paa1019</i> was observed up to 60%. Genetic mapping combined with Mutmap analysis revealed that <i>LOC_Os03g20380</i> harbored a single-bp substitution (C to T) that altered its transcript length. This gene encodes calcineurin B-like protein-interacting protein kinase 31 (OsCIPK31) localized into the cytoplasm, and is preferentially expressed in transport tissues of rice. Complementation of <i>paa1019</i> by transferring the open reading frame of <i>LOC_Os03g20380</i> from YXB reversed the mutant phenotype, and conversely, gene editing by knocking out of <i>OsCIPK31</i> in YXB results in PAA phenotype. Our results support that <i>OsCIPK31</i> plays an important role in panicle development. We found that dysregulation is caused by the disruption of <i>OsCIPK31</i> function due to excessive accumulation of ROS, which ultimately leads to cell death in rice panicle. <i>OsCIPK31</i> and MAPK pathway might have a synergistic effect to lead ROS accumulation in response to stresses. Meanwhile the PAA distribution is related to IAA hormone accumulation in the panicle. Our study provides an understanding of the role of OsCIPK31 in panicle development by responding to various stresses and phytohormones.