Overexpression of a Na ⁺ /H ⁺ antiporter confers salt tolerance on a freshwater cyanobacterium, making it capable of growth in sea water

Abstract

The salt tolerance of a freshwater cyanobacterium, Synechococcus sp. PCC 7942, transformed with genes involved in the synthesis of a Na ؉ ͞H ؉ antiporter, betaine, catalase, and a chaperone was examined. Compared with the expression of betaine, catalase, and the chaperone, the expression of the Na ؉ ͞H ؉ antiporter gene from a halotolerant cyanobacterium (ApNhaP) drastically improved the salt tolerance of the freshwater cyanobacterium. The Synechococcus cells expressing ApNhaP could grow in BG11 medium containing 0.5 M NaCl as well as in sea water, whereas those expressing betaine, catalase, and the chaperone could not grow under those conditions. The coexpression of ApNhaP with catalase or ApNhaP with catalase and betaine did not further enhance the salt tolerance of Synechococcus cells expressing ApNhaP alone when grown in BG11 medium containing 0.5 M NaCl. Interestingly, the coexpression of ApNhaP with catalase resulted in enhanced salt tolerance of cells grown in sea water. These results demonstrate a key role of sodium ion exclusion by the Na ؉ ͞H ؉ antiporter for the salt tolerance of photosynhetic organisms.Aphanothece halophytica ͉ genetic engineering

Analysis of expression of aquaporins and Na+/H+ transporters in tomato colonized by arbuscular mycorrhizal fungi and affected by salt stress

“…It should also be mentioned that, by contrast, an enhanced expression by AMF has been reported for another aquaporin in roots of Medicago truncatula (Krajinski et al, 2000). Overexpression of Na + /H + antiporters in plants or microorganisms renders them more tolerant to salt stress (Zhang et al, 2001;Waditee et al, 2002). Thus, analyzing expression of two Na + /H + antiporter genes in dependence on salt and mycorrhizal colonization was of particular interest in the present study.…”

Properties of the halophyte microbiome and their implications for plant salt tolerance

“…A key role of Na + exclusion by different types of Na + /H + antiporters were also described for the cyanobacterium Synechococcus sp. PCC7942 (Waditee et al 2002), the cyanobacterium Aphanothec halophytica (Wutipraditkul et al 2005) and the bacterium Alkalimonas amylolytica (Zhong et al 2012). In A. amylolytica the Na + /H + antiporter encoding gene AaNhaD was able to increase salt tolerance in transgenic tobacco BY-2 cells indicating that AaNhaD even in plant cells functions as a pH-dependent tonoplast Na + /H + antiporter, thus, presenting a new avenue for the genetic improvement of salinity/alkalinity tolerance (Zhong et al 2012).…”

Halotolerant Cyanobacterium Aphanothece halophytica Contains an Na+-dependent F1F0-ATP Synthase with a Potential Role in Salt-stress Tolerance

“…Expression (10). For salt stress experiments, Synechococcus cells were subcultured in BG11 medium as described above but supplemented with 50 g ml Ϫ1 streptomycin.…”