P5CR基因的进化及其在木薯中的表达分析

Evolution Analysis of P5CR and Expression Analysis of P5CR Genes in Cassava

吡咯啉-5-羧酸还原酶(P5CR)催化脯氨酸合成途径的最后一步反应,在植物逆境胁迫响应中起重要作用。采用生物信息学方法从木薯(Manihot esculenta Crantz)等45个已完成基因组测序的植物中共鉴定出54条P5CR序列,分析其在不同物种的分布和序列特征;用MEGA软件构建Neighbor-joining系统进化树;采用实时荧光定量PCR技术分析MeP5CR在不同组织和胁迫处理下的表达特性。P5CR在内含子长度上差别较大,而在氨基酸长度、外显子数目、等电点和分子量等方面差别不大。在大多数植物(如木薯)中,P5CR有且仅有1个拷贝,表明P5CR在进化上比较保守,且是单基因起源。然而,在某些植物(如大豆、苹果等)中存在2-3个拷贝,说明在物种进化的过程中P5CR发生了多次重复事件,并将它们归纳为3种进化模式。表达分析表明,MeP5CR在叶片、须根和储藏根中表达量最高,而在叶柄和茎中的表达量最低。MeP5CR表达量受低温胁迫诱导、但被干旱胁迫抑制。MeP5CR在转录水平参与木薯干旱和低温胁迫响应。

Pyrroline-5-carboxylate reductase（P5CR）,which catalyzes the final reaction of proline biosynthesis pathway,plays animportant role in plant stress response. Totally 54 P5CR sequences were identified from 45 genome sequence available species（includingcassava）by bioinformatic method,and their distribution and sequence characteristics were analyzed;neighbor-joining phylogenetic treeswas constructed by MEGA software;and the expression levels of MeP5CR were evaluated in different tissues and in response to abiotic stressesby quantitative real-time PCR（q RT-PCR）method. The results showed that P5CR had a large difference in intron length,but there was nosignificant difference in amino acid length,exon number,isoelectric point,and molecular weight. There is only one copy of P5CR in mostplants,such as in cassava,indicating that P5CR is evolutionarily conserved and originated from a single gene. However,there are 2-3 copiesP5CR genes in some plants such as soybean and apple,indicating that P5CR genes experienced several duplication events during the evolutionprocesses,and totally three different evolutionary patterns were revealed. Expression analysis revealed that MeP5CR expressed the highest inleaf,fibrous root,and storage root,but expressed the lowest in stem and petiole. MeP5CR was significantly induced by cold stress but greatlyinhibited by drought stress. These findings suggest that MeP5CR is involved in drought and cold stresses at the transcriptional level,and it canbe treated as a candidate to further study its functions in abiotic stress in cassava.