Involvement of GA3-oxidase in inhibitory effect of nitric oxide on primary root growth in Arabidopsis

Abstract

Both NO and GAs are essential for regulating various physiological processes and stress responses in plants. However, the interaction between these two molecules remains unclear. We investigated the distinct response patterns of Arabidopsis thaliana Col-0 and GA synthesis functional deficiency mutants to NO by measuring root length. To investigate underlying mechanisms, we detected bioactive GA content using UHPLC-ESI-MS/MS, assessed the accumulation of ROS by chemical staining Arabidopsis roots. We also conducted RNA-seq analysis and compared results between Col-0 and ga3ox1, with and without SNP (as NO donor) treatment. Phenotypic results revealed that the inhibitory effect of NO on primary roots of Arabidopsis was primarily mediated by GA3-oxidase, rather than GA20-oxidase or GA2-oxidase. The content of GA₃ decreased in Col-0 treated with SNP, whereas this decrease was not observed in ga3ox1. The deficiency of GA3-oxidase alleviated the buildup of H₂ O₂ in roots when treated with SNP. We identified 222 DEGs. GO annotation of these DEGs revealed that all top 20 GO terms were related to stress responses. Moreover, three DEGs were annotated to GA-related processes (DDF1, DDF2, EXPA1), and seven DEGs were associated with root development (RAV1, RGF2, ERF71, ZAT6, MYB77, XT1, and DTX50). In summary, NO inhibits primary root growth partially by repressing GA3-oxidase catalysed GA₃ synthesis in Arabidopsis. ROS, Ca²⁺ , DDF1, DDF2, EXPA1 and seven root development-related genes may be involved in crosstalk between NO and GAs.

Keywords: GA3-oxidase; RNA-seq; nitric oxide; primary root.