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Vacuolar processing enzyme is up‐regulated in the lytic vacuoles of vegetative tissues during senescence and under various stressed conditions
Author(s) -
Kinoshita Tetsu,
Yamada Kenji,
Hiraiwa Nagako,
Kondo Maki,
Nishimura Mikio,
HaraNishimura Ikuko
Publication year - 1999
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1046/j.1365-313x.1999.00497.x
Subject(s) - vacuole , arabidopsis , biology , microbiology and biotechnology , gene expression , lytic cycle , methyl jasmonate , gene , biochemistry , arabidopsis thaliana , saccharomyces cerevisiae , genetics , mutant , virus , cytoplasm
Summary Vacuolar processing enzyme (VPE) has been shown to be responsible for maturation of various seed proteins in protein‐storage vacuoles. Arabidopsis has three VPE homologues; βVPE is specific to seeds and αVPE and γVPE are specific to vegetative organs. To investigate the activity of the vegetative VPE, we expressed the γVPE in a pep4 strain of the yeast Saccharomyces cerevisiae and found that γVPE has the ability to cleave the peptide bond at the carbonyl side of asparagine residues. An immunocytochemical analysis revealed the specific localization of the γVPE in the lytic vacuoles of Arabidopsis leaves that had been treated with wounding. These findings indicate that γVPE functions in the lytic vacuoles as the βVPE does in the protein‐storage vacuoles. The βVPE promoter was found to direct the expression of the β‐glucuronidase reporter gene in seeds and the root tip of transgenic Arabidopsis plants. On the other hand, both the αVPE and γVPE promoters directed the expression in senescent tissues, but not in young intact tissues. The mRNA levels of both αVPE and γVPE were increased in the primary leaves during senescence in parallel with the increase of the mRNA level of a senescence‐associated gene ( SAG2 ). Treatment with wounding, ethylene and salicylic acid up‐regulated the expression of αVPE and γVPE , while jasmonate slightly up‐regulated the expression of γVPE . These gene expression patterns of the VPEs were associated with the accumulation of vacuolar proteins that are known to respond to these treatments. Taken together, the results suggest that vegetative VPE might regulate the activation of some functional proteins in the lytic vacuoles.