Our previous studies revealed that methane (CH ) induces adventitious rooting in cucumber. However, the corresponding molecular mechanism is still elusive. In this work, we discovered that CH triggered the accumulation of nitric oxide (NO) and thereafter cucumber adventitious rooting, mimicking the inducing effects of sodium nitroprusside (SNP) and NONOate (two NO-releasing compounds). Above mentioned responses were sensitive to NO scavenger(s), showing that the accumulation of NO and adventitious root development were respectively impaired. Inhibitor test and biochemical analysis suggested that endogenous NO mainly produced by mammalian NO synthase-like enzyme and diamine oxidases (DAO), might be required for adventitious root formation elicited by CH . Molecular evidence confirmed that CH -mediated induction of several marker genes responsible for adventitious root development, including CsDNAJ-1, CsCDPK1, CsCDPK5, cell division-related gene CsCDC6, and two auxin signaling genes, CsAux22D-like and CsAux22B-like, was casually dependent on NO signaling. The possible involvement of S-nitrosylation during the mentioned CH responses was preliminarily illustrated. Taken together, through pharmacological, anatomical and molecular approaches, it is suggested that NO might be involved in CH -induced cucumber adventitious rooting, and CH -eliciated NO-targeted proteins might be partially modulated at transcriptional and post-translational levels. Our work may increase the understanding of the mechanisms underlying CH -elicited root organogenesis in higher plants.

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Osmotic stress influences root system architecture, and polar auxin transport (PAT) is well established to regulate root growth and development. However, how PAT responds to osmotic stress at the molecular level remains poorly understood. In this study, we explored whether and how the auxin efflux carrier PIN-FORMED3 (PIN3) participates in osmotic stress-induced root growth inhibition in Arabidopsis (Arabidopsis thaliana).We observed that osmotic stress induces a HD-ZIP II transcription factor-encoding gene HOMEODOMAIN ARABIDOPSIS THALIANA2 (HAT2) expression in roots. The hat2 loss-offunction mutant is less sensitive to osmotic stress in terms of root meristem growth. Consistent with this phenotype, whereas the auxin response is downregulated in wild-type roots under osmotic stress, the inhibition of auxin response by osmotic stress was alleviated in hat2 roots. Conversely, transgenic lines overexpressing HAT2 (Pro35S::HAT2) had shorter roots and reduced auxin accumulation compared with wild-type plants.PIN3 expression was significantly reduced in the Pro35S::HAT2 lines. We determined that osmotic stress-mediated repression of PIN3 was alleviated in the hat2 mutant because HAT2 normally binds to the promoter of PIN3 and inhibits its expression.Taken together, our data revealed that osmotic stress inhibits root growth via HAT2, which regulates auxin activity by directly repressing PIN3 transcription.

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A new flavonoid angelioue (1), and five known compounds, cuminatanol (2), myricetin (3), epigallocatechin (4), taxifolin (5) and dihydromyricetin (6), with good antibacterial and cytotoxic activities were isolated from the callus extract of Ampelopsis grossedentata.