A Brassica napus transcript encoding a protein related to the Künitz protease inhibitor family accumulates upon water stress in leaves, not in seeds

Abstract

A cDNA clone encoding a Brassica napus drought-induced 22 kDa (BnD22) protein has been isolated and characterized. The BnD22 transcript accumulated in response to drought reversibly, and to other conditions of leaf water deficit such as rapid water stress or salt acclimation, but not to cold acclimation or heat shock. Exogenously applied abscisic acid induced both changes in leaf morphology similar to the drought-adaptive response and a pronounced accumulation of the BnD22 mRNA. In control and drought-adapted plants, the BnD22 transcript was expressed in an organ-specific manner: the mRNA level was highest in leaves, low in hypocotyls and undetectable in roots. Sequence analysis indicates that the BnD22 protein is related to the Künitz family of protease inhibitors. In contrast to most members of this family, and also to most polypeptides expressed in vegetative tissues upon drought, the BnD22 mRNA was absent in seeds, before or during the seed desiccation phase. The BnD22 gene represents a new class of genes which are strictly induced in vegetative tissues upon environmental stress, and its pattern of expression shows that the responses to water deficit differ, at least partially, in seeds and in leaves.

Molecular Cloning and Functional Expression of a Water-soluble Chlorophyll Protein, a Putative Carrier of Chlorophyll Molecules in Cauliflower

“…WSCP is highly hydrophilic, may be located in chloroplasts (34), is able to extract Chls from thylakoid pigment proteins (Fig. 4), and is induced under stress conditions (3,7,8). All these features of WSCP are in accord with the hypothesis that WSCP serves as a Chl carrier.…”

“…The nucleotide sequence of the cDNA confirmed that it encoded WSCP of cauliflower and BnD22 of rapeseed (3,7,8). For further confirmation of the identity of the cDNA, we performed RACE-reverse transcription PCR with a sense DNA primer (5Ј-ATGAAGACTTTTTT-TCTAG-3Ј) corresponding to the NH 2 -terminal residues of the BnD22 precursor, MKTFFL (7).…”

“…For further confirmation of the identity of the cDNA, we performed RACE-reverse transcription PCR with a sense DNA primer (5Ј-ATGAAGACTTTTTT-TCTAG-3Ј) corresponding to the NH 2 -terminal residues of the BnD22 precursor, MKTFFL (7). An amplified fragment was cloned and sequenced.…”

“…In recent studies, it was suggested that the WSCPs from cauliflower (3) and Brussels sprouts (4) may be identical to a drought-induced 22-kDa protein in rapeseed, BnD22, which possesses a motif of the Kü nitz-type proteinase inhibitor family (7,8). Although WSCPs from cauliflower (3), rapeseed (3), Brussels sprouts (4), and L. virginicum (Y. Oka, K. Fujiyama, H. Satoh, K. Nakayama, and M. Okada (1996) DDBJ accession no.…”

Water-Soluble Chlorophyll Protein in Brassicaceae Plants is a Stress-Induced Chlorophyll-Binding Protein

“…Because a cDNA sequence of a heat-stress induced protein in cabbage (Annamalai and Yanagihara 1999), BocHS1, is identical to that of cauliflower WSCP, BocHS1 is considered to be a WSCP itself in cabbage. It has been reported that a drought responsive protein in rapeseed (Downing et al 1992), BnD22, is identical to WSCP (Nishio and Satoh 1997). A WSCP homolog in Arabidopsis thaliana has been sequenced as a probable drought-induced protein (T9N14.19 in A. thaliana chromosome 1).…”