Sequences of the Cotton Group 2 LEA/RAB/Dehydrin Proteins Encoded by Lea3 cDNAs

Abstract

Listen

Translate article

The 18 cloned cotton Lea (late embryogenesis-abundant) mRNAs are a diverse group encoding proteins that may be desiccation protectants (5). Lea mRNAs are coordinately induced by ovule abscission in cotton embryos during the postabscission stage before desiccation (5) and in cultured embryos by desiccation, osmotic stress, or exposure to ABA, a plant hormone that may be a transducer of water-related stresses (6). Homologs of the cotton Lea3 cDNA clone D 1I (1) have been identified as rab (responsive to ABA) in rice seedlings exposed to ABA or salt (10) and maize embryos and calli exposed to ABA (9), Dhn (dehydrin) in maize and barley seedlings exposed to water stress (2), pcD27-04 and pcC6-19 in dried leaves and ABA-treated calli of the resurrection plant Craterostigma plantagineum (7), RSLEA2 in dry seeds of radish (8), and TAS14 in tomato seedlings exposed to osmotica or ABA (4). Although the organization and amino acid sequences of these Group 2 LEA/RAB/dehydrin proteins are highly conserved, the carboxy terminus of the cotton D 1I LEA3 protein is singularly divergent. Because the nucleotide sequence of D 11 could encode a more typical terminus if there were frame-shift mutations or sequencing errors (2), we have independently determined the sequence of Dl I and, for comparative purposes, also determined the entire nucleic acid sequence of D147b and part of D71 and D131, three additional Lea3 cDNA clones (Table I). The nucleotide and deduced amino acid sequences of D147b and a comparison with those of Dl I are presented in Figure 1. We note that the published sequence of DIl (1) contains two relatively unimportant errors. First, D 1I contains two additional nucleotides at the 5' end that were not previously reported. Second, D 1 contains a G at D 11 nucleotide 353, not a C as previously reported. The latter cor' Supported by National Institutes of Health grant No. GM29495 to G.A.G. and U.S. Department of Agriculture/Cooperative State Research Service grant No. 91-37100-6615 to T.J.C.