Functional analysis of PrkA - a putative serine protein kinase from Mesorhizobium alhagi CCNWXJ12-2 - in stress resistance.
BACKGROUND
Serine/threonine protein kinases are highly conserved kinases with a wide distribution in microbes and with multiple functions. Mesorhizobium alhagi CCNWXJ12-2, a α-proteobacterium which could be able to form symbiosis with Alhagi sparsifolia in northwest of China, contains a putative PrkA-family serine protein kinase, PrkA. In our previous study, the expression of prkA was found to be downregulated in high-salt conditions. To elucidate the function of M. alhagi PrkA, a prkA deletion mutant was constructed and the phenotypes of the mutant were analyzed.


RESULTS
The salt and alkaline tolerance and antioxidant capacity of the wild-type strain and the prkA deletion mutant was measured. Our results showed that the deletion mutant had higher salt and alkaline tolerance than the wild-type strain. The total cellular Na+content was measured and showed no significant difference between the wild-type strain and the mutant. The prkA deletion mutant also showed a higher H2O2tolerance than the wild-type strain. Therefore the activities of antioxidant enzymes were measured. Catalase activity was similar in the wild-type and the deletion mutant, while the superoxide dismutase activity in the mutant was higher than that in the wild-type.


CONCLUSIONS
We firstly analyze the function of a serine protein kinase, PrkA, in M. alhagi. Our data indicate that PrkA could reduce the survival of M. alhagi under environmental stress and deletion of prkA dramatically improved the salt and alkaline tolerance and antioxidant capacity of M. alhagi.
State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, College of Life Sciences, Northwest A & F University, Yangling, Shaanxi, 712100, China.
Xiaodong
X
Liu
State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, College of Life Sciences, Northwest A & F University, Yangling, Shaanxi, 712100, China.
Yantao
Y
Luo
State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, College of Life Sciences, Northwest A & F University, Yangling, Shaanxi, 712100, China.
Zhefei
Z
Li
State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, College of Life Sciences, Northwest A & F University, Yangling, Shaanxi, 712100, China. weigehong@nwsuaf.edu.cn.
Gehong
G
Wei
Antioxygenation; Na+ concentration measurement; Salt resistance; Serine protein kinase
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