Higher Novel L-Cys Degradation Activity Results in Lower Organic-S and Biomass in than the Related Saltwort, .

and are almost identical halophytes whose edible succulent shoots hold promise for commercial production in saline water. Enhanced sulfur nutrition may be beneficial to crops naturally grown on high sulfate. However, little is known about sulfate nutrition in halophytes. Here we show that (ecotype RN) exhibits a significant increase in biomass and organic-S accumulation in response to supplemental sulfate, whereas (ecotype VM) does not, instead exhibiting increased sulfate accumulation. We investigated the role of two pathways on organic-S and biomass accumulation in and : the sulfate reductive pathway that generates Cys and l-Cys desulfhydrase that degrades Cys to HS, NH, and pyruvate. The major function of -acetyl-Ser-(thiol) lyase (OAS-TL; EC 2.5.1.47) is the formation of l-Cys, but our study shows that the OAS-TL A and OAS-TL B of both halophytes are enzymes that also degrade l-Cys to HS. This activity was significantly higher in than in , especially upon sulfate supplementation. The activity of the sulfate reductive pathway key enzyme, adenosine 5'-phosphosulfate reductase (APR, EC 1.8.99.2), was significantly higher in than in These results suggest that the low organic-S level in is the result of high l-Cys degradation rate by OAS-TLs, whereas the greater organic-S and biomass accumulation in is the result of higher APR activity and low l-Cys degradation rate, resulting in higher net Cys biosynthesis. These results present an initial road map for halophyte growers to attain better growth rates and nutritional value of and .