Abstract
BackgroundSerine/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.ResultsThe 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 H2O2 tolerance 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.ConclusionsWe 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.
Highlights
Serine/threonine protein kinases are highly conserved kinases with a wide distribution in microbes and with multiple functions
We have previously found that the expression of prkA was downregulated in high-salt conditions through RNA-Seq validated by RT-qPCR [6]
In Mycobacterium tuberculosis, the pknE deletion mutant showed higher tolerance to acidic stress, sodium dodecyl sulfate (SDS), and kanamycin than the wild-type, which means pknE is involved in stress adaptation [13]
Summary
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. Mesorhizobium alhagi CCNWXJ12-2 is a highly salt-tolerant and alkali-tolerant rhizobium which can form nodules with the desert plant Alhagi sparsifolia [3]. The nitrogen-fixing symbiosis formed between rhizobia and legumes can decrease the damage to plants caused by soil salinity; there are an increasing number of studies on salt-tolerant rhizobia and their mechanism(s) of salt resistance [4, 5]. PrkA is a highly conserved serine protein kinase with a wide distribution in bacteria and archaea [7]. Subsequent research showed that a yeaG deletion mutant showed no significant difference in salt tolerance and pH adaptation compared with the wild-type strain [12]
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