木薯及其他植物P5CS基因进化及表达分析

Evolution and Expression Analysis of P5CS Genes in Cassava and Other Plants

该研究采用生物信息学的方法,从木薯等31个已完成基因组测序的植物中,共鉴定出84个吡咯啉-5-羧酸合成酶(P5CS)基因,并对其进行系统发育分析。结果表明:(1)P5CS在内含子长度上差别较大,而在氨基酸长度、外显子数目、等电点和分子量上差别不大。(2)由于发生基因重复,在大多数单子叶和双子叶植物中都有2个P5CS,而且在单子叶和双子叶植物中均发现P5CS1基因聚类在一组,而P5CS2基因聚类在另一组,支持P5CS1和P5CS2基因是独立起源,且该重复事件发生在单子叶和双子叶植物分化之前。(3)在某些植物(如蒺藜苜蓿、大豆等)中存在3~7个P5CS基因,表明在单子叶和双子叶植物分化之后P5CS基因又发生了多次重复事件,并将它们归纳为4种进化模式。(4)木薯中有2个P5CS基因,表达分析显示,MeP5CS1和MeP5CS2在叶片、叶柄、茎、须根和储藏根中均可检测到,其中MeP5CS1在叶片中表达较高,而MeP5CS2在茎和储藏根中表达较高。(5)干旱胁迫下,MeP5CS1仅在第一片完全展开叶中被显著诱导,而MeP5CS2在第一片完全展开叶和老叶中均能被显著诱导;低温胁迫下,MeP5CS1和MeP5CS2在不同组织中均能被显著诱导,但具有不同的表达模式。研究表明,木薯的MeP5CS1和MeP5CS2基因在转录水平受到干旱、低温等非生物胁迫的调控。

A total 84 pyrroline-S-carboxylate synthetase （PSCS） genes were identified from 31 genome sequence available plants by using bioinformatics methods, and their phylogenetic analyses were performed. The results revealed that： （1） PSCS had a large difference in intron length, but there was no significant difference in amino acid length, exon number, isoelectric point, and molecular weight. （2） Due to the oc- currence of gene duplication, there were two PSCS in most monocot and dicot plants. （3） Moreover, in both monocot and dieot plants, P5CS1 genes were clustered in one group, while P5CS2 genes were clus- tered in another group, supporting that P5CS1 and P5CS2 of independent origin and the duplication event occurred before the divergence of monocot and dicot plants. In some plants （such as Medicago truncatula and soybean） there were 3--7 PSCS genes, indicating that the duplication events of PSCS genes also oc- curred several times after the divergence of monocot and dicot plants, and totally four different evolution- ary patterns were revealed. （4） There were two P5CS genes in cassava. Expression analysis revealed that MeP5CS1 and MePSCS2 were expressed in leaf, petiole, stem, fibrous root and storage root. （5） Of which, MeP5CS1 was highly expressed in leaf, while MePSCS2 was highly expressed in stem and storage root. Under drought stress, MePSCS1 was significantly induced in the first fully expanded leaf, while MeP5CS2 was significantly induced in the first fully expanded leaf and bottom leaf. Under cold stress, both MeP5CS1 and MePSCS2 were significantly induced in different tissues, but they exhibited different expression patterns. These results indicated that MePSCS1 and MeP5CS2 were involved in the regulation of abiotic stresses （e. g. , drought and cold） at the transcriptional level.