水稻OsANT亚家族成员的结构、表达特征及其对逆境胁迫的响应

Structure characterization,expression and stress response analyses of OsANT subfamily genes in rice

植物氨基酸转运蛋白直接负责氨基酸的跨膜转运过程,分属于3个家族的不同亚家族,其中ANT亚家族成员主要负责芳香族氨基酸和中性氨基酸的转运。本文对水稻ANT亚家族成员的系统进化树、跨膜结构和蛋白保守基序特征进行了分析,对成员的时空表达特征和逆境下的响应情况进行了研究,并利用氨基酸吸收缺陷型酵母分析了OsANT的氨基酸吸收特性。结果表明,OsANT亚家族的4个成员在进化上与单子叶植物玉米和高粱的关系较近,而与双子叶植物拟南芥和番茄的关系较远;蛋白保守基序特征分析表明,OsANT亚家族成员与其他物种中的ANT成员有6个共有的保守基序;基因表达分析表明,OsANT亚家族基因在不同组织和部位之间具有差异性表达的特征,可能协同参与了水稻体内氨基酸的利用过程;逆境下基因表达量的分析表明,OsANT亚家族基因可能参与到多种逆境的响应过程中,其中OsANT1(根部)对热胁迫、OsANT2对氮素营养水平、OsANT3(地上部)对盐胁迫以及OsANT4(根部)对镉胁迫响应较为明显;然而,利用氨基酸吸收缺陷型酵母的互补实验表明,OsANT亚家族成员对多种氨基酸均无明显的吸收活性。该研究对于解析OsANT亚家族成员的功能以及逆境下氨基酸转运分配的机制提供了重要的线索和基础。

Amino acid transporters are directly responsible for the transmembrane transport of amino acids within plants, and they belong to different subfamilies of three major families. The ANT subfamily members are mainly responsible for the transport of aromatic and neutral amino acids. This research focuses on the phylogenetic tree, structure characterization, expression and stress response of OsANT subfamily genes. The amino acid absorption characteristics of OsANT subfamily members are also analyzed. The results showed that OsANT display a closer evolutionary relationship to the ANT members from monocotyledon such as Zea mays and Sorghum bicolor than to the ANT members from dicotyledonous plants such as Arabidopsis thaliana and Lycopersicon esculentum. Conserved motifs analysis using MEME tool identified six conserved motifs among ANT proteins of rice and other species. Gene expression analysis showed that four OsANT genes were differentially expressed among different tissues and organs, which implied that they might work together for utilizing amino acids within rice plants. Further analysis found that OsANT subfamily genes might involve in adversity stresses response, as the expression level of OsANT1 in roots was effectively affected by heat stress, expression level of OsANT2 changed by nitrogen treatment, salt induced OsANT3 expression in shoots and cadmium stress induced OsANT4 expression in roots, respectively. However, all OsANT subfamily members failed to show any transport activity for the tested amino acid in heterologous complementation experiments using a yeast amino acid transporter mutant. This study provides valuable clues for further uncover the biological and physiological functions of OsANT members, and will be also helpful for researching on the mechanisms of transport and distribution of amino acids under stresses.