Brassinosteroids is involved in methane-induced adventitious root formation via inducing cell wall relaxation in marigold

Background Methane (CH 4 ) and brassinosteroids (BRs) are important signaling molecules involved in a variety of biological processes in plants. Results Here, marigold ( Tagetes erecta L. ‘Marvel’) was used to investigate the role and relationship between CH 4 and BRs during adventitious root (AR) formation. The results showed a dose-dependent effect of CH 4 and BRs on rooting, with the greatest biological effects of methane-rich water (MRW, CH 4 donor) and 2,4-epibrassinolide (EBL) at 20% and 1 μmol L − 1 , respectively. The positive effect of MRW on AR formation was blocked by brassinoazole (Brz, a synthetic inhibitor of EBL), indicating that BRs might be involved in MRW-regulated AR formation. MRW promoted EBL accumulation during rooting by up-regulating the content of campestanol (CN), cathasterone (CT), and castasterone (CS) and the activity of Steroid 5α-reductase (DET2), 22α-hydroxylase (DWF4), and BR-6-oxidase (BR6ox), indicating that CH 4 could induce endogenous brassinolide (BR) production during rooting. Further results showed that MRW and EBL significantly down-regulated the content of cellulose, hemicellulose and lignin during rooting and significantly up-regulated the hydrolase activity, i.e. cmcase, xylanase and laccase. In addition, MRW and EBL also significantly promoted the activity of two major cell wall relaxing factors, xyloglucan endotransglucosylase/hydrolase (XTH) and peroxidase, which in turn promoted AR formation. While, Brz inhibited the role of MRW on these substances. Conclusions BR might be involved in CH 4 -promoted AR formation by increasing cell wall relaxation.