LRXs (leucine-rich repeat extensins) are chimeric cell wall proteins containing an N-terminal leucine-rich repeat (LRR) and a C-terminal extensin domain. Increasing evidences suggest that LRXs family genes play important roles in pollen germination and pollen tube growth in Arabidopsis thaliana. However, the functions of rice (Oryza sativa L.) LRX genes in pollen development remain poorly understood. Bioinformatics analysis showed that the rice LRX gene family consist of eight members, namely OsPEX3, OsLRX3 and OsLRX5 located on chromosome 1, OsLRX1, OsLRX3, OsLRX2,OsPEX1 and OsPEX2 located on chromosome 2, 5, 6, 11 and 12, respectively. The OsPEX1 gene is preferentially expressed in rice anther, suggesting that it may be involved in the regulation of pollen development. Next, we further investigated the role of the OsPEX1 gene in rice by knockdown of its expression using an RNAi approach. The OsPEX1 RNAi transgenic lines showed a significant decrease in seed setting rate (10%~30%) due to pollen sterility. Further quantitative RT-PCR analysis indicated that the OsPEX1 gene was significantly down-regulated in the RNAi transgenic lines. The results indicate that the OsPEX1plays an important role in the regulation of rice pollen development. Further studies on this gene could provide insights on the molecular and genetic mechanisms in this developmental process.
类伸展蛋白(Leucine-Rich Repeats Extensins, LRX)是一类细胞壁嵌合蛋白,其N端包含一个LRR (leucine-rich repeats)结构域,C端含Extensins结构域。研究表明,LRX基因家族在拟南芥(Arabidopsis thaliana)花粉萌发和花粉管生长过程中具有重要作用,而水稻(Oryza sativa L.) LRX基因家族是否在调控花粉发育方面具有保守的生物学功能尚不清楚。本研究首先进行了生物信息学分析,结果显示,水稻LRX基因家族包括8个成员,OsPEX3、OsLRX3、OsLRX5位于水稻第1号染色体;OsLRX1、OsLRX3、OsLRX2、OsPEX1和OsPEX2分别位于第2、第5、第6、第11和第12号染色体,其中OsPEX1基因在花粉中高表达,暗示OsPEX1可能参与了花粉发育调控。为此,本研究采用RNAi技术进一步研究了OsPEX1基因对花粉发育的影响。结果表明,OsPEX1基因的RNAi转基因植株花粉败育,结实率仅为10%-30%。qRT-PCR分析显示,这些RNAi转基因植株OsPEX1基因表达量显著低于野生型,而且其表达量越低花粉育性亦随之降低。上述研究结果表明,水稻OsPEX1基因是水稻花粉发育的重要基因,该基因的克隆和功能分析有助于进一步阐明水稻花粉发育调控的分子遗传学机制。.
Keywords: leucine-rich repeats extensins; pollen fertility; rice.