玉米的叶片坏死斑点(lethal leaf-spot 1,Lls1)基因及其拟南芥中的同功能基因已证明编码叶绿素分解代谢中的关键酶脱镁叶绿酸氧化酶(pheide a oxygenase,PaO)．为了深入研究大豆叶片衰老过程中叶绿素分解代谢的调控机制,从大豆中克隆了玉米Lls1的同源基因,其cDNA全长1817bp,命名为GmLls1(GenBank登录号：DQ154009)．序列分析表明,该基因与拟南芥、玉米、豇豆和番茄等的Lls1及其同功能基因具有很高的同源性,其编码蛋白含有典型的Rieske[2Fe-2S]结构域、非亚铁血红素铁结合域和C-末端CXXC基序,这些都是PaO功能蛋白所具有的典型结构特征．RT-PCR结果显示,在大豆叶片自然衰老、人工黑暗诱导衰老和子叶衰老3个系统中,GmLls1基因都表现出明显的衰老上调趋势．进一步分析发现,在因敲减类受体蛋白激酶rlpk2基因而导致衰老延缓的大豆转基因叶片中,GmLls1的表达显著下降,而在因过表达rlpk2而导致加速衰老的转基因叶片中,GmLls1的转录本积累明显增加,暗示RLPK2介导的信号途径可能参与调控GmLls1在大豆叶片衰老过程中的表达,而rlpk2-RNAi转基因离体叶片光照下表现出lls1突变体典型的斑状失绿坏死表型则进一步支持了上述推论．
Leaf senescence that occurs in the last stage of leaf development is a genetically programmed process. It is very significant to isolate the upstream components in the senescence signaling pathway and to elucidate the molecular mechanisms that control the initiation and progression of leaf senescence. In this study, full-length cDNAs of three receptor-like protein kinase genes, designated rlpkl, rlpk2 and rlpk3, were cloned from artificially-induced senescent soybean （Glycine max L.） primary leaves （GenBank accession AY687390, AY687391, AF338813）. The deduced amino acid sequences indicated that they belonged to a receptor-like kinase family. Each of rlpkl and rlpk2 encodes a leucine-rich repeat （LRR） receptor-like protein kinase. They both comprise a typical signal peptide, several LRR motifs, a single-pass transmembrane domain, and a cytoplasmic protein kinase domain. No typical extracellular domain of RLPK3 was predicted. Organ-specific expression pattern analysis by reverse-transcription polymerase chain reaction （RT-PCR） revealed higher expression levels of the three genes in cotyledons, roots and flowers. Phylogenetic analysis indicated that RLPK1 and RLPK2 belonged to an independent branch, whereas RLPK3 shared common nodes with several known RLKs responding to ablotic and biotic stresses. The evident alternations of expression profiles of rlpkl and rlpk2 induced by the artificial senescence-inducing treatment implied involvements of these two RLKs in regulating soybean leaf senescence.
Yuan-Yuan MaLi-Wen ZhangPeng-Li LiRui GanXiao-Ping LiRen ZhangYong WangNing-Ning Wang
＜正＞Receptor protein kinases comprise multigene families. They are plasma membrane-bound and play an important ...
Xiaoping Li, Rui Gan, Yuanyuan Ma, Pengli Li Liweng Zhang, Ren Zhang, Ningning Wang(Department of Botany and Ecology, Nan Kai University, Tianjin 300071
