性别决定基因TASSELSEED2在水稻中的功能歧化性浅析

花器官的发育不仅影响农作物的生产,通过性别决定产生单性花的机制亦是重要的基础理论问题。TASSELSEED2基因是与JA合成有关的调控玉米单性雄花产生的性别决定基因,对一些植物中TS2同源基因的表达分析表明TS2蛋白可能在进化过程中产生了功能歧化。为探究TS2蛋白在进化过程中其功能是否发生了歧化,首先通过生物信息学手段对水稻和玉米的TS2基因进行了比较分析,分子进化分析表明,TS2基因在一些植物中可能并不仅仅局限于抑制雌蕊发育的性别决定功能。因此,猜测两性花植物水稻中的TS2可能具有其他功能。利用蛋白质三维结构预测软件,发现水稻TS2基因编码典型的SDR蛋白,含有保守的GASGIG和YTASK基序,其作用底物可能与玉米TS2蛋白类似。启动子分析表明OsTS2和玉米TS2的激素应答元件存在差别。随后,利用RNA-seq数据进行了OsTS2与玉米TS2的组织器官表达分析,并利用实时荧光定量技术考察外源Me JA喷施处理对OsTS2与玉米TS2基因表达的影响。结果表明,OsTS2主要在花序中表达,经外源MeJA处理后其表达量明显升高;而玉米TS2在雄穗分化关键期的叶片中表达量最高,其表达量基本不受外源Me JA影响。OsTS2与玉米TS2表达方面的差异提示水稻TS2可能具有与玉米TS2不同的功能,为深入了解TS2在两性花植物中的功能提供了线索。

The Divergent Role of Sex Determination Gene TASSELSEED2 in Rice

The development of floral organs is crucial for the production of crops,in which the formation of unisexual flowers by sex-determination is one of the important theoretic issues.The TASSELSEED2 gene is a JA-synthesis gene which regulates the formation of staminate flower in maize.Previous studies showed that TS2 genes of grasses might adopt new or divergent functions during evolution.In order to get insights into the divergent role of TS2,compared the protein structure of rice TS2 with maize TS2 by bioinformatic tools.The results showed that OsTS2 encodes a typical SDR protein which contains a conserved GASGIG motif and YTASK motif.The substrate catalyzed by OsTS2 protein was also predicted to be similar with that by maize TS2 protein.Further examined the expression pattens of OsTS2 and maize TS2 in different tissues.RNA-seq data showed that OsTS2 mainly expressed in the inflorescence of rice.In accord with JA and other hormone regulatory elements found in the promoter of OsTS2,the increased expression of OsTS2 was obviously observed by qPCR in MeJA-treated rice.Whereas,the expression of maize TS2 was mainly detected in 8-leaf stage of maize rather than in inflorescence,and its expression was not affected by exogenous methyl jasmonate.Taken together,these results provide a clue that OsTS2 might recruit a divergent role during evolution.