Disruption of the Expression of the Cinnamoyl–CoA Reductase (CCR) Gene OsCCR18 Causes Male Sterility in Rice (Oryza sativa L. japonica)

Abstract

The biological process of anther development is very complex. It remains largely unclear how the cinnamoyl–CoA reductase (CCR) encoding genes function in the regulation of anther development in plants. Here, we establish that the CCR family gene OsCCR18 is essential for maintaining male fertility in rice. The OsCCR18 transcripts were greatly abundant in the panicles at the S4 and S5 developmental stages in rice. The subcellular localization of OsCCR18 proteins was in the nucleus of the rice. The knockout of the OsCCR18 gene resulted in a severely abnormal degradation of the tapetum as well as the abnormal development of granular Ubisch bodies, leading to the inability to form normal pollen in the mutants. Compared with the wild–type (WT) rice, the osccr18 mutants had no visible pollen grains and had entirely male sterility. Furthermore, several anther development–related genes, including OsPDA1, OsDTD, OsC6, OsACOS12, OsTDR, OsWDA1, OsDPW, OsCYP703A3, and OsNOP, were significantly lower expressed in the panicles at the stages from S5 to S8 in the osccr18 mutants than in the WT plants. Additionally, hundreds of genes involved in phenylpropanoid biosynthesis, fatty acid synthesis and metabolism exhibited distinct expression patterns between the WT and mutants, which may be crucial for controlling anther development in rice. These findings add a new regulatory role to CCR family gene–mediated male fertility in rice.