title: Identification and functional characterization of a leucine-rich repeat receptor-like kinase gene that is involved in regulation of soybean leaf senescence.
abstract: We report here the cloning and characterization of a soybean receptor-like kinase (RLK) gene, designated GmSARK (Glycine max senescence-associated receptor-like kinase), which is involved in regulating leaf senescence. The conceptual protein product of GmSARK contains typical domains of LRR receptor-like kinases: a cytoplasmic domain with all the 11 kinase subdomains, a transmembrane domain and an extracelullar domain containing 9 Leucine-Rich Repeat (LRR) units that may act as a receptor. The expression of GmSARK in soybean leaves was up-regulated in all the three tested senescence systems: senescing cotyledons, dark-induced primary leaf senescence and the natural leaf senescence process after florescence. Furthermore, the RNA interference (RNAi)-mediated knocking-down of GmSARK dramatically retarded soybean leaf senescence. A more complex thylakoid membrane system, higher foliar level of chlorophyll content and a very remarkable delay of senescence-induced disintegration of chloroplast structure were observed in GmSARK-RNAi transgenic leaves. A homolog of maize lethal leaf-spot 1 gene, which has been suggested to encode a key enzyme catalyzing chlorophyll breakdown, was isolated and nominated Gmlls1. The expression level of Gmgtr1 gene, which encodes a key enzyme of chlorophyll synthesis, was also analyzed. It was found that Gmlls1 was up-regulated and Gmgtr1 was down-regulated during senescence in wild-type soybean leaves. However, both of the up-regulation of Gmlls1 and down-regulation of Gmgtr1 were retarded during senescence of GmSARK-RNAi transgenic leaves. In addition, over-expression of the GmSARK gene greatly accelerated the senescence progression of CaMV 35S:GmSARK transgenic plants. Taken together, these results strongly suggested the involvement of this LRR-RLK in regulation of soybean leaf senescence, maybe via regulating chloroplast development and chlorophyll accumulation. Multiple functions of GmSARK besides its regulation of leaf senescence were also discussed.
authors.affiliation: Department of Plant Biology and Ecology, Nankai University, Tianjin, 300071, PR China.
authors.forename: Xiao-Ping
authors.initials: XP
authors.lastname: Li
authors.forename: Rui
authors.initials: R
authors.lastname: Gan
authors.forename: Peng-Li
authors.initials: PL
authors.lastname: Li
authors.forename: Yuan-Yuan
authors.initials: YY
authors.lastname: Ma
authors.forename: Li-Wen
authors.initials: LW
authors.lastname: Zhang
authors.forename: Ren
authors.initials: R
authors.lastname: Zhang
authors.forename: Yong
authors.initials: Y
authors.lastname: Wang
authors.forename: Ning Ning
authors.initials: NN
authors.lastname: Wang
mesh_terms: D000595:Amino Acid Sequence; D002736:Chloroplasts / Q000502:physiology / Q000648:ultrastructure; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics; D035264:Flowers / Q000201:enzymology / Q000235:genetics / Q000254:growth & development; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D046529:Microscopy, Electron, Transmission; D008969:Molecular Sequence Data; D018515:Plant Leaves / Q000201:enzymology / Q000235:genetics* / Q000502:physiology; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D030821:Plants, Genetically Modified; D011494:Protein Kinases / Q000235:genetics* / Q000378:metabolism; D034622:RNA Interference; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D013025:Glycine max / Q000201:enzymology / Q000235:genetics* / Q000502:physiology; D020524:Thylakoids / Q000648:ultrastructure
chemical_list: D018076:DNA, Complementary; D010940:Plant Proteins; D011494:Protein Kinases