A NOVEL BETAINE ALDEHYDE DEHYDROGENASE GENE FROM Medicago sativa AND ITS EXPRESSION UNDER SALINITY

Abstract

SUMMARYBetaine aldehyde dehydrogenase (BADH) has been reported from several plant species mostly halophytes as the most important enzyme responsible for salinity tolerance. We investigated the expression of BADH gene along with ionic and enzymatic accumulations in an alfalfa cultivar, Medicago sativa cv. Gara-Yonjeh, widely cultivated in saline soils across East-Azerbaijan Province, Iran. Five different NaCl concentrations of 0, 50, 100, 150 and 200 mM were examined using 30 seeds for each treatment. The Na + , K + , Ca 2+ and proline concentration were measured in cotyledon and young roots of seven-day-old seedlings under salinity stresses and controls. Total RNA was extracted and the mRNA levels of P5CS2 (∆ 1 -pyrroline-5-carboxylate synthetase) and BADH (hereafter MsP5CS2 and MsBD1, respectively) were determined using semiquantitative RT-PCR analysis. MsBD1mRNA was reverse-transcribed and then was amplified using PCR. The amplified MsBD1 DNAs were cloned. Our results showed that 150mM NaCl was the stress threshold concentration for the young seedlings. The accumulation of the cations and proline significantly increased by increasing NaCl concentration from 0 to 150mM. The mRNA levels of MsP5CS2 and MsBD1 increased in both cotyledons and roots at 150mM compared to control. A 1518 basepair cDNA fragment coding for MsBD1, and its proposed 505-amino acid sequences were characterized in Medicago sativa cv. GaraYonjeh. These DNA and amino acid sequences showed high homology with BADH gene/amino acid sequences previously reported from several other plant species. Our study shows that genic and ionic mechanisms are simultaneously employed in this cultivar to cope with salinity.