Exploring Different Roles of StWRKY4 and StWRKY56 in Transgenic Potato Against Salt Stress

WRKY transcription factors play an important role in transcriptional reprogramming associated with plant abiotic stress responses. In this study, the role of <i>Solanum tuberosum</i> (<i>S. tuberosum</i>; <i>St</i>) WRKY transcription factors <i>StWRKY4</i> and <i>StWRKY56</i> were explored in response to salt stress by generating transgenic potato lines using RNAi. The results showed that the total chlorophyll content in transgenic <i>StWRKY4</i> was 6.1 mg/g at 200 mM after 35 days; however, in <i>StWRKY56</i>, an elevated 12.6 mg/g total chlorophyll was observed which indicated different operating mechanisms of these <i>St</i>WRKY transcription factors under salt stress. Proline content increased to 1.0 mg/g in <i>StWRKY4</i> while it decreased to 0.54 mg/g in <i>StWRKY56</i> as compared to their respective control plants after 35 days at 200 mM of salt stress. For Na⁺/K⁺ ratios, <i>StWRKY4</i> and <i>StWRKY56</i> showed 32.3 and 5.5 values, respectively, in silenced plants under similar conditions. This shows contrasting trends in <i>StWRKY4</i> and <i>StWRKY56</i> for Na⁺/K⁺. However, the expression analyses of <i>StSOS1</i>s were found to be upregulated, whereas for <i>StNHX3</i>s these were found to be downregulated in <i>StWRKY4</i> and <i>StWRKY56</i> under salt stress. Thus, this study, for the first time, demonstrated the different but critical roles of <i>StWRKY4</i> and <i>StWRKY56</i> for fine-regulating salt stress tolerance in complex signaling network of potato plant.