The Carrot Phytoene Synthase 2 (<i>DcPSY2</i>) Promotes Salt Stress Tolerance through a Positive Regulation of Abscisic Acid and Abiotic-Related Genes in <i>Nicotiana tabacum</i>
Orlando Acevedo | Rodrigo A. Contreras | Claudia Stange
<i>Background:</i> Carotenoids, which are secondary metabolites derived from isoprenoids, play a crucial role in photo-protection and photosynthesis, and act as precursors for abscisic acid, a hormone that plays a significant role in plant abiotic stress responses. The biosynthesis of carotenoids in higher plants initiates with the production of phytoene from two geranylgeranyl pyrophosphate molecules. Phytoene synthase (PSY), an essential catalytic enzyme in the process, regulates this crucial step in the pathway. In <i>Daucus carota</i> L. (carrot), two <i>PSY</i> genes (<i>DcPSY1</i> and <i>DcPSY2</i>) have been identified but only <i>DcPSY2</i> expression is induced by ABA. Here we show that the ectopic expression of <i>DcPSY2</i> in <i>Nicotiana tabacum</i> L. (tobacco) produces in L3 and L6 a significant increase in total carotenoids and chlorophyll <i>a</i>, and a significant increment in phytoene in the T<sub>1</sub>L6 line. Tobacco transgenic T<sub>1</sub>L3 and T<sub>1</sub>L6 lines subjected to chronic NaCl stress showed an increase of between 2 and 3- and 6-fold in survival rate relative to control lines, which correlates directly with an increase in the expression of endogenous carotenogenic and abiotic-related genes, and with ABA levels. <i>Conclusions:</i> These results provide evidence of the functionality of <i>DcPSY2</i> in conferring salt stress tolerance in transgenic tobacco T<sub>1</sub>L3 and T<sub>1</sub>L6 lines.
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