Heterologous Expression of Argininosuccinate Synthase From Enhances the Acid Resistance of .

can survive well in wine (an acid-stress environment) and dominate malolactic fermentation (MLF). To demonstrate a possible role of argininosuccinate synthase gene () in the acid tolerance response of , a related gene was inserted into a plasmid pMG36e and heterologously expressed in SL09, a wine isolate belonging to a species of relevant importance in MLF. The expression levels of the gene in were analyzed by RT-qPCR, argininosuccinate synthase (ASS) activity and cell properties (amino acids, pH, H-ATPase activity, and ATP levels) were determined at pH 3.7 in comparison with that at pH 6.3. Results showed that the recombinant strain SL09 (pMG36e) exhibited stronger growth performance compared with the control strain (without gene), and the expression levels of , , , the citrate and malate metabolic genes were apparently increased under acid stress. In addition, the recombinant strain exhibited 11.0-, 2.0-, 1.9-fold higher ASS activity, H-ATPase activity and intracellular ATP level, compared with the corresponding values for control strain during acid-stresses condition, which may take responsible for the acid tolerance enhancement of the recombinant strain. This is the first work report on heterologous expression of gene, and the results presented in this study will be beneficial for the research on acid stress response of