A branched-chain amino acid aminotransferase gene isolated from Hordeum vulgare is differentially regulated by drought stress

Abstract

Differential display was used to isolate cDNA clones showing differential expression in response to ABA, drought and cold in barley seedling shoots. One drought-regulated cDNA clone (DD12) was further analyzed and found to encode a branched-chain amino acid aminotransferase (HvBCAT-1). A genomic clone was isolated by probing the Morex BAC library with the cDNA clone DD12 and the structure of Hvbcat-1 was elucidated. The coding region is interrupted by six introns and contains a predicted mitochondrial transit peptide. Hvbcat1 was mapped to chromosome 4H. A comparison was made to rice and Arabidopsis genes to identify conserved structural patterns. Complementation of a yeast (Saccharomyces cerevisiae) double knockout strain revealed that HvBCAT-1 can function as the mitochondrial (catabolic) BCATs in vivo. Transcript levels of Hvbcat-1, increased in response to drought stress. As the first enzyme in the branched-chain amino acid (BCAA) catabolic pathway, HvBCAT-1 might have a role in the degradation of BCAA. Degradation of BCAA could serve as a detoxification mechanism that maintains the pool of free branched-chain amino acids at low and non toxic levels, under drought stress conditions.

LC-HRMS Based Non-Targeted Metabolomic Profiling of Wheat (<I>Triticum aestivum</I> L.) under Post-Anthesis Drought Stress

“…Increased accumulation of tryptophan in wheat under drought is also supported by previous studies [21] [50], and Arabidopsis [51], and similar result was found in this study. Taylor et al (2004) reported that branched chain amino acids are a source of alternate energy when Arabidopsis plants were under sugar starvation, which is a common phenomenon under stress [52].…”

The Sucrose Starvation Signal Mediates Induction of Autophagy- and Amino Acid Catabolism-Related Genes in Cowpea Seedling

“…The enzymes are also involved in the degradation of BCAA to provide an alternative carbon source under stress conditions in plants, animal and bacteria. Barley BCATs and Arabidopsis BCAT2 are induced by drought stress and sucrose starvation, respectively [19,20]. The observation that sucrose starvation enhanced the expression of VuBCAT2 prompted us to propose a hypothesis that an increased degradation of BCAA by BCAT results in inactivation of cowpea TOR, in tern, leading to induction of autophagy via ATG1-ATG13 cascade.…”

“…Recently, low energy stresses such as reduced photosynthesis and/or sucrose starvation appeared to induce daramatic change of amino acid catabolism for asparagine biosynthesis by inducing the expression of asparagine synthase (AtASN1), proline dehydrogenase1 (AtProDH), and branched chain aminoacid transaminase (AtBCAT2) [18,19]. Among cowpea homlog genes amino acid catabolic-related enzymes, VuASN1 (TC7410), VuProDH (TC15194) and VuBCAT2 (TC3413) were identified to have the highest similarites of 82%, 62% and 62% in deduced amino acid sequences to AtASN1 (At3g47340), AtProDH (At3g30775) and AtBCAT2 (At1g10070), respectively.…”

A branched-chain aminotransferase may regulate hormone levels by affecting KNOX genes in plants

“…Surprisingly, it was found that AtBCAT-4 participates in the chain elongation pathway of Met-derived glucosinolate biosynthesis, which has a close evolutionary relationship to the Leu biosynthesis pathway (Schuster et al 2006). A newly identiWed BCAT gene from barley, HvBCAT-1, is inducible by drought stress (Malatrasi et al 2006).…”

“…There is a small family of BCAT genes in plants, which have been characterized in some species such as Solanum tuberosum (potato), Arabidopsis and Hordeum vulgare (barley) (Campbell et al 2001;Diebold et al 2002;Malatrasi et al 2006). Two BCAT genes (StBCAT-1, StBCAT-2) isolated from S. tuberosum are diVerentially expressed.…”