Abstract
Aldehyde dehydrogenase (ALDH) carries out oxidation of toxic aldehydes using NAD+/NADP+ as cofactors. In the present study, we performed a genome-wide identification and expression analysis of genes in the ALDH gene family in Brassica rapa. A total of 23 ALDH genes in the superfamily have been identified according to the classification of ALDH Gene Nomenclature Committee (AGNC). They were distributed unevenly across all 10 chromosomes. All the 23 Brassica rapa ALDH (BrALDH) genes exhibited varied expression patterns during treatments with abiotic stress inducers and hormonal treatments. The relative expression profiles of ALDH genes in B. rapa showed that they are predominantly expressed in leaves and stem suggesting their function in the vegetative tissues. BrALDH7B2 showed a strong response to abiotic stress and hormonal treatments as compared to other ALDH genes; therefore, it was overexpressed in heterologous hosts, E. coli and yeast to study its possible function under abiotic stress conditions. Over-expression of BrALDH7B2 in heterologous systems, E. coli and yeast cells conferred significant tolerance to abiotic stress treatments. Results from this work demonstrate that BrALDH genes are a promising and untapped genetic resource for crop improvement and could be deployed further in the development of drought and salinity tolerance in B. rapa and other economically important crops.
Highlights
Molecular crosstalk between different stress responsive pathways seems to be an efficient survival strategy of plants to overcome and sustain against unfavorable environmental conditions during their growth and development
SMART, ScanProsite and InterPro analyses revealed the characteristic presence of Aldehyde dehydrogenase (ALDH) cysteine (PS00070, IPR016160) and glutamic (PS00687, IPR016160) residues, which are intermittently found in the proteins encoded by the ALDH superfamily, and were identified in 11 out of the 23 ALDH genes encoded proteins in B. rapa
Recent availability of the complete sequence of B. rapa genome has helped in the annotation and identification of 23 ALDH genes located on 10 chromosomes in this crop species
Summary
Molecular crosstalk between different stress responsive pathways seems to be an efficient survival strategy of plants to overcome and sustain against unfavorable environmental conditions during their growth and development. The production of reactive aldehydes occurs through both enzymatic and non-enzymatic pathways[3] It is a well-known phenomenon for over a decade that aldehyde molecules, when produced at disproportionate/imbalanced concentrations would have deleterious effects on plant metabolism causing lipid peroxidation, impaired cellular homeostasis, enzyme inactivation, DNA damage, and cell death[4,5]. Previous studies suggested that the over-expression of ALDH genes in Arabidopsis plants enhanced their tolerance to different environmental stress factors[6,11,12,13]. Kotochoni et al (2006) showed that Arabidopsis plants overexpressing ALDH311 and ALDH7B4 genes exhibited enhanced protection against lipid peroxidation and salinity stress In addition to their roles in different stresses, Rf2a, a mitochondrial ALDH gene has been reported for its involvement in maintaining male fertility and anther formation in maize[15].
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