Abstract
Glycinebetaine (GB) is an important compatible solute for salinity tolerance in many plants. In this study, we analyzed the enzymatic activity and the expression level of betaine aldehyde dehydrogenase (BADH), an important enzyme that catalyzes the last step in the GB synthesis in Leymus chinensis, a GB-hyperaccumulating graminaceous halophyte, and compared with those of barley, a graminaceous glycophyte. We have isolated cDNAs for two BADH genes, LcBADH1 and LcBADH2. LcBADH1 has a putative peroxisomal signal peptide (PTS1) at its C-terminus, while LcBADH2 does not have any typical signal peptide. Using immunofluorescent labeling, we showed that BADH proteins were localized to the cytosol and dot-shaped organelles in the mesophyll and bundle sheath cells of L.chinensis leaves. The affinity of recombinant LcBADH2 for betaine aldehyde was comparable to other plant BADHs, whereas recombinant LcBADH1 showed extremely low affinity for betaine aldehyde, indicating that LcBADH2 plays a major role in GB synthesis in L. chinensis. In addition, the recombinant LcBADH2 protein was tolerant to NaCl whereas LcBADH1 wasn’t. The kinetics, subcellular and tissue localization of BADH proteins were comparable between L. chinensis and barley. The activity and expression level of BADH proteins were higher in L. chinensis compared with barley under both normal and salinized conditions, which may be related to the significant difference in the amount of GB accumulation between two plants.Electronic supplementary materialThe online version of this article (doi:10.1186/s40064-015-0997-4) contains supplementary material, which is available to authorized users.
Highlights
Salinity is one of the biggest factors which limits the productivity of crops (Boyer 1982)
Cloning of cDNAs for LcBADH1 and LcBADH2 genes in L. chinensis To isolate betaine aldehyde dehydrogenase (BADH) cDNAs from L. chinensis, we constructed a cDNA library from leaves of salt-stressed L. chinensis and cloned BADH cDNAs by PCR using degenerate primers which were designed on the basis of the highly conserved amino acid sequences from several plants’ BADH as described in Methods
LcBADH2 has cysteine at position 444 that is critical for high affinity to betaine aldehyde (Díaz-Sánchez et al 2012) whereas LcBADH1 possesses a low betaine aldehyde affinity isoleucine at the corresponding position
Summary
Salinity is one of the biggest factors which limits the productivity of crops (Boyer 1982). In order to survive and continue growth, plants have developed many defense mechanisms which allow them to adapt to unsuitable environments. One of these mechanisms is the accumulation of compatible solutes. Compatible solutes differ among plant species and include sugar alcohols, amino acids and their derivatives, tertiary sulphonium compounds and quaternary ammonium compounds (Rhodes & Hanson 1993; Bohnert & Jensen 1996). Glycinebetaine (GB) is one of the most important compatible solutes. GB is present in bacteria, cyanobacteria, animals, and several plant families
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