Molecular cloning and characterization of a granulin-containing cysteine protease SPCP3 from sweet potato (Ipomoea batatas) senescent leaves.
Granulins are a family of evolutionarily ancient proteins that are involved in regulating cell growth and division in animals. In this report a full-length cDNA, SPCP3, was isolated from senescent leaves of sweet potato (Ipomoea batatas). SPCP3 contains 1389 nucleotides (462 amino acids) in its open reading frame, and exhibits high amino acid sequence homologies (ca. 64-73.6%) with several plant granulin-containing cysteine proteases, including potato, tomato, soybean, kidney bean, pea, maize, rice, cabbage, and Arabidopsis. Gene structural analysis shows that SPCP3 encodes a putative precursor protein. Via cleavage of the N-terminal propeptide, it generates a protein with 324 amino acids (from the 139th to the 462nd amino acid residues), which contains two main domains: the conserved catalytic domain with the putative catalytic residues (the 163rd Cys, 299th His and 319th Asn) and the C-terminal granulin domain (from the 375th to the 462nd amino acid residues). Semi-quantitative RT-PCR and protein gel blot hybridization showed that SPCP3 gene expression was enhanced significantly in natural senescent leaves and in dark- and ethephon-induced senescent leaves, but was almost undetectable in mature green leaves, veins, and roots. Phylogenic analysis showed that SPCP3 displayed close association with a group of plant granulin-containing cysteine proteases which have been implied to be involved in programmed cell death. In conclusion, sweet potato SPCP3 is a functional, senescence-associated gene. Its mRNA and protein levels were significantly enhanced in natural and induced senescing leaves. The physiological role and/or function of SPCP3 associated with programmed cell death during leaf senescence were also discussed.
Chen
Hsien-Jung
HJ
Department of Horticulture, Chinese Culture University, 111 Taipei, Taiwan, ROC.
Huang
Dong-Jiann
DJ
Hou
Wen-Chi
WC
Liu
Jih-Shiou
JS
Lin
Yaw-Huei
YH
D000595:Amino Acid Sequence; D017209:Apoptosis / Q000235:genetics; D001483:Base Sequence; D003001:Cloning, Molecular; D003546:Cysteine Endopeptidases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D003624:Darkness; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D036341:Intercellular Signaling Peptides and Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D027723:Ipomoea batatas / Q000201:enzymology / Q000235:genetics*; D008969:Molecular Sequence Data; D009943:Organophosphorus Compounds / Q000494:pharmacology; D010802:Phylogeny; D018515:Plant Leaves / Q000201:enzymology / Q000235:genetics / Q000502:physiology; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D000077153:Progranulins; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment
D036341:Intercellular Signaling Peptides and Proteins; D009943:Organophosphorus Compounds; D010940:Plant Proteins; D000077153:Progranulins; D003546:Cysteine Endopeptidases; C005073:ethephon