To evaluate the role of H2S in lateral root formation, the gene expression of putative SlDES1 encoding DES was analyzed. Results of real-time RT-PCR revealed that the expression abundance of SlDES1 ( Fig. 3B) was significantly decreased upon NPA pretreatment, which were consistent with the decreased DES activity and H2S content ( Fig. 3A). By contrast, the addition of NaHS together with NPA could reverse above responses. NaHS alone also triggered inducing effects. However, no significant differences were observed when NaHS was applied with or without NAA pretreatment, and both of which were comparable to the phenotypes in the lateral root formation ( Fig. 1). In addition, microscopical analyses showed that the treatment with NPA might block LRP formation, while NAA- and NaHS-induced LRP presented a similar accelerated anatomic structure ( Fig. 3C).