Late
embryogenesis abundant (Lea) proteins accumulate in maturing seeds after many of the storage compounds have been synthesized, and they are considered relevant to maturation. We report here the molecular organization and expression of BnLea3-1, a novel Group 3 Lea
gene from
Brassica napus. BnLea3-1 contains a
coding region of 798 bp, sharing 84.4% homology at the
amino acid level with Lea76 of B. napus. Two tandem 11-mer repeats are truncated from the
coding region of BnLea3-1, compared to the 13 conserved 11-mer repeats of Lea76. Substitutions of
consensus residues are found at various positions within the 11-mer repeats. A 1561 bp 5′ flanking
promoter fragment of BnLea3-1 fused to E. coli-
glucuronidase (GUS)
coding region conferred seed-specific GUS expression in stable transgenics of B. napus, tobacco and in transiently-transformed pea. A −137 bp
minimal promoter preceding the first
transcription start site, identified through progressive deletions from the upstream was sufficient for basal GUS expression in the seeds and in leaves treated with ABA. Deletion studies indicate the presence of enhancing elements located between −137 bp to −742 bp and suppressing elements located between −742 and −1561 bp. BnLea3-1 expression in seeds precedes that of Lea76. Unlike other Group 3 Lea members including HVA1 and Dc3, BnLea3-1 is active in seeds and responsive weakly in vegetative tissues to ABA and
methyl jasmonate (MeJA) but not to stress treatments. Possible functions of BnLea3-1 and another member of the Group 3 Lea family BnLea3-2 in
embryo development is discussed.