Regulatory Mechanism Of GSNOR On Lateral Root Development In Arabidopsis Thaliang

S-nitrosoglutathione reductase (GSNOR) is a class of conserved proteins in organisms involved in nitric oxide (NO) metabolism and balance by restoring nitrosoglutathione (GSNO), thus regulate plant growth and disease resistance. In Arabidopsis, GSNOR null allele mutants hot5-2 (Col background) and hot5-4 (WS background) exhibited serious deficiency of lateral roots, meanwhile complementary lines of GSNOR in hot5-2 could completely recover normal phenotypes. Therefore, GSNOR was an important gene controlling lateral roots number in Arabidopsis. Protein location of GSNOR showed that GSNOR was abundantly expressed and enriched in lateral roots, indicating that GSNOR was directly involved in the occurrence and development of lateral roots. Expression of auxin reporter DR5::GFP and DII-VENUS showed that mutants had no obvious auxin accumulation in lateral roots to form auxin concentration gradients which involved in lateral roots occurrence and development. Further physiological experiments demonstrated that both endogenous and exogenous NO could change auxin content and normal development of lateral roots, and the effect was especially strong in GSNOR null mutants, indicating that GSNOR could affect auxin polar transport so as to regulate the lateral root development. We also found that NO enhanced auxin signaling obviously in plant based on the following results:1) Accumulation of NO could facilitate degradation of IAA proteins.2) Exogenous NO increased the expression of key genes such as ALF4 and LBD18 in lateral roots. In summary, the present research about the key protein GSNOR in NO metabolism suggested that NO played an important role in the appearance of lateral roots. Under low concentration, NO increased the number of lateral roots by auxin; with an increasing concentration of NO, the polar auxin transport was destroyed and failed to form an auxin concentration gradient in the lateral root primordial, leading to the inhibition of the occurrence and development of lateral roots. While GSNOR played a central regulatory role in the interaction between NO and auxin in the process.