Effect of uniconazole to soybean seed priming treatment under drought stress at VC stage

Studying the mechanism of drought stress in soybean root at vegetative cotyledon (VC) stage by soaking seeds with uniconazole revealed new insights into soybean stress physiology. Therefore, a completely random pot experiments with different time gradients for water cut-off (24, 48, 72, 96 and 120 h, respectively) were carried out with uniconazole (0.4 mgL^-1) with respect to morphological, microscopic, ultramicroscopic, physiological, and molecular studies on varieties Hefeng55 (H50, drought tolerant variety) and Kenfeng16 (K16, drought susceptible variety). Results revealed that uniconazole effectively alleviated the inhibition on root growth caused by drought stress, increased the number of root tips, significantly reduced lignification of vessels, alleviated the damage of mitochondria and nucleus caused by drought stress, further strengthened osmotic adjustment system and antioxidant system, especially when the soil moisture content was less than 14%, broke expression restriction of IAA due to drought stress, and inhibited GA₃ generation; finally, we found that high-intensity drought stress significantly increased the expression levels of GmNAC003, GmNAC004, GmNAC015, GmNAC020, GmHK07, GmRR01, GmRR02 and GmRR16 genes relating to drought tolerance, while uniconazole had a significant inhibitory effect on GmNAC003, GmNAC004, GmNAC015, GmNAC020, GmRR01, GmRR02 and GmRR16 genes. Our results provided a reference for the mechanism of drought resistance in legume and the effect of uniconazole on alleviating drought stress.