摘要:
植物在长期进化过程中演化出不同机制来适应环境中的各种胁迫,如盐碱、干旱等.该研究从拟南芥T-DNA插入突变体库中筛选到一个对盐反应不敏感的突变株系eto(enhanced tolerance to osmotic stress),种子萌发和幼苗生长试验表明eto突变株系早期生长发育对盐胁迫不敏感.TAIL-PCR分析表明eto突变株系中T-DNA插入在拟南芥1号染色体上(BAC F3M18的27502位置),位于拟南芥At1g77740基因起始密码子前487 bp处,该基因编码磷脂酰肌醇-4-磷酸5-激酶(AtPIP5K2),共分离分析表明T-DNA插入与盐不敏感性紧密连锁.以野生型拟南芥总RNA为模板,克隆拟南芥AtPIP5K2<基因cDNA,其开放读码框为2 265 bp,编码755个氨基酸.与已报道物种PIPKs基因氨基酸序列比较分析表明,AtPIP5K2<与植物PIPKs基因氨基酸相似性高达62%~75%,但与其他生物物种PIPKs基因之间的氨基酸相似性仅为33%~37%;AtPIP5K2<推导的氨基酸序列中含有植物PIPKs基因所具有的高度保守区域“PIPKc”、“MORN repeat”.进一步分析表明AtPIP5K2基因在拟南芥根及莲座叶片中表达量较强,并且由于T-DNA的插入,使eto突变株系与野生型相比,其AtPIP5K2基因过量表达,表明AtPIP5K2<基因编码的产物可能参与调节拟南芥适应盐胁迫的调节反应.
Abstract:
One mutant line named eto(enhanced tolerance to osmotic stress),with salt tolerance was screened from a T-DNA insertion mutant collection of Arabidopsis thaliana.TAIL-PCR analysis showed that T-DNA tag insertion in the eto was located at nucleotide 27502 in BAC F3M18,upstream(at position-487 relative to the translation initiation codon) of gene At1g77740(encoding a putative phosphatidylinositol-4-phosphate 5-kinase,AtPIP5K2).In addition to a reduced rate of seed germination,NaCl also inhibited the growth and the greening of cotyledons of wild-type seedlings,but not the eto mutant.This inserted mutation co-segregated closely with the eto phenotype.AtPIP5K2 was amplified by RT-PCR from the total RNA of wild type plants.Sequence analysis revealed that the cDNA full-length is 2 265 bp encoding a protein of 755 amino acids.When deduced amino acid sequences were compared with homologous sequences from other organisms,AtPIP5K2 was found sharing much higher sequence similarity(62%—75%) with plant PIPKs genes than with PIPKs genes of other organisms(33%—37% similarity).In addition,AtPIP5K2 also contained two highly conserved motifs "PIPKc","MORN repeat",which were identical to those of other PIPKs from plants.Another analysis not only indicated that AtPIP5K2 transcript was expressed predominantly in roots and rosette leaves,but also showed the insertion resulted in higher accumulation of the AtPIP5K2 in mutant plants,and this change may play an essential role in the tolerance to the osmotic stress.
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