Unusual sequences of group 3 LEA mRNA inducible by maturation or drying in soybean seeds

Abstract

Two cDNA clones, pGmPM8 and pGmPM10, which correspond to two mRNA species in mature or dry soybean seeds, were characterized. The deduced proteins, based on DNA sequence analysis, have a molecular mass of 49 and 51 kDa for pGmPM8 and pGmPM10, respectively. These two cDNA clones share a high homology with an amino acid identity of about 90% between the two deduced proteins. Both proteins appear to be extremely hydrophilic except at their N-termini that contain a 29 amino acid hydrophobic region at the N-terminus and the sizes of proteins decrease after co-incubating with ER membranes. These two proteins contain more than 30 similar, contiguous repeats of 11 amino acids, which is characteristic of group 3 LEA proteins. The mRNAs corresponding to pGmPM8 and pGmPM10 were expressed at high levels in dried or mature soybean seeds, but not in fresh immature seeds. The RNAs were also present in abscisic acid (ABA) treated leaves or cultured cells, and in tissues subjected to water stress or low temperatures.

The continuing conundrum of the LEA proteins

“…Rather, they are expressed in a number of subcellular compartments, including chloroplasts, mitochondria, the nucleus, and in the cytoplasm (Table 4). There is also at least one example (Ukaji et al 2001) of two closely related group 3 LEA proteins located in the endoplasmic reticulum (ER) and two others that have an N-terminal signal peptide suggesting translocation of the ER membrane; the latter proteins were shown to be reduced in Mr slightly when produced in the presence of microsomes, consistent with cleavage of the signal peptide (Hsing et al 1995). Other signal peptides are likely to control targetting to mitochondria, plastids, etc., as appropriate.…”

The Enigmatic LEA Proteins and Other Hydrophilins

“…Expression analysis of plant proteins in this group, as well as information available from transcriptomic projects, shows their accumulation in mature seeds and in response to dehydration, salinity, or low temperatures Cattivelli and Bartels, 1990;Hsing et al, 1995;Romo et al, 2001). Some members also respond to hypoxia (Siddiqui et al, 1998) or to high-excitation pressure imposed by high light (NDong et al, 2002).…”

Genome of the Extremely Radiation-Resistant Bacterium Deinococcus radiodurans Viewed from the Perspective of Comparative Genomics

“…The Lea-76 family belongs to group 3 of LEA proteins, which also are well-characterized and widespread desiccationinduced proteins in plants (46,58,99,140). The main sequence feature in these proteins is a tandem repeat of a distinct 11-mer motif, in which the amino acids at positions 1, 2, 5, and 9 are nonpolar and the rest are charged or amide residues (e.g., AAQKTKDYASD in the Lea-76 protein from soybean; GI, 421875) (58).…”