title: The rice OsSAG12-2 gene codes for a functional protease that negatively regulates stress-induced cell death.
abstract: Senescence is the final stage of plant development. Although expression of most of the genes is suppressed during senescence, a set of genes referred as senescence-associated genes (SAGs) is induced. Arabidopsis thaliana SAG12 (AtSAG12) is one such gene that has been mostly studied for its strict association with senescence. AtSAG12 encodes a papain-like cysteine protease, expressed predominantly in senescence-associated vacuoles. Rice genome contains multiple AtSAG12 homologues (OsSAGs). OsSAG12-1, the closest structural homologue of AtSAG12, is a negative regulator of developmental and stress-induced cell death. Proteolytic activity has not been established for any SAG12 homologues in vitro. Here, we report that OsSAG12-2, the second structural homologue of AtSAG12 from rice, codes for a functional proteolytic enzyme. The recombinant OsSAG12-2 protein produced in Escherichia coli undergoes autolysis to generate a functional protease. The matured OsSAG12-2 protein shows 27 percent trypsin-equivalent proteolytic activity on azocasein substrate. Dark-induced senescence activates OsSAG12-2 expression. Down-regulation of OsSAG12-2 in the transgenic artificial miRNA lines results in enhanced salt- and UV-induced cell death, even though it does not affect cell viability in the stress-free condition. Our results show that OsSAG12-2 codes for a functional protease that negatively regulates stress-induced cell death in rice.
authors: School of Life Sciences, Jawaharlal Nehru University, New Delhi 110 067, India.
authors: Subaran
authors: S
authors: Singh
authors: Anupriya
authors: A
authors: Singh
authors: Ashis Kumar
authors: AK
authors: Nandi
mesh_terms: D000375:Aging / Q000235:genetics; D017360:Arabidopsis / Q000235:genetics; D029681:Arabidopsis Proteins / Q000096:biosynthesis / Q000235:genetics*; D016923:Cell Death / Q000187:drug effects / Q000528:radiation effects; D003546:Cysteine Endopeptidases / Q000096:biosynthesis / Q000235:genetics*; D018506:Gene Expression Regulation, Plant / Q000187:drug effects / Q000528:radiation effects; D012275:Oryza / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development; D018515:Plant Leaves / Q000235:genetics / Q000254:growth & development; D030821:Plants, Genetically Modified / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development; D012965:Sodium Chloride / Q000633:toxicity; D013312:Stress, Physiological / Q000187:drug effects / Q000235:genetics* / Q000528:radiation effects; D014466:Ultraviolet Rays
chemical_list: D029681:Arabidopsis Proteins; D012965:Sodium Chloride; C402082:SAG12 protein, Arabidopsis; D003546:Cysteine Endopeptidases