Circadian and senescence-enhanced expression of a tobacco cysteine protease gene |
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Authors: | Ueda Tadamasa Seo Shigemi Ohashi Yuko Hashimoto Junji |
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Institution: | (1) National Institute of Agrobiological Resources, 2-1-2 Kannondai, Tsukuba, Ibaraki, 305-8602, Japan;(2) CREST, Japan Science and Technology Corporation, Chiyodaku, Tokyo, 101-0062, Japan |
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Abstract: | A cDNA clone encoding a cysteine protease was isolated from a tobacco cDNA library, utilizing as a probe a PCR fragment obtained from degenerated primers based on the conserved sequences of plant cysteine protease genes. A putative protein encoded by the clone NTCP-23 had an amino acid sequence with significant similarities to those of plant senescence-associated cysteine proteases and mammalian cathepsin H. Northern blot analysis showed that NTCP-23 mRNA is expressed in all organs and the mRNA and protein expression is enhanced during natural senescence. We propose that NTCP-23 is responsible for amino acid remobilization especially in senescencing leaves. Furthermore, it was found that the mRNA expression follows a circadian rhythm and is reduced by continuous darkness, wounding and hypersensitive reaction (HR). NTCP-23 is the first cysteine protease whose mRNA expression has been shown to be temporarily reduced by wounding. |
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Keywords: | circadian rhythm cysteine protease (cysteine endopeptidases EC 3 4 22) senescence tobacco (Nicotiana tabacum) wounding |
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