DEAD-box RNA helicase 6 regulates drought and abscisic acid stress responses in rapeseed (Brassica napus).

DEAD-box RNA helicase is a major subfamily of RNA helicases with vital roles played in plant growth, development, and plant-environment interactions. RNA helicase 6 in rapeseed (Brassica napus) (BnRH6) is a member of DEAD-box RNA helicase. While previous research has demonstrated the role of BnRH6 in salt stress regulation, the involvement of BnRH6 in drought stress adaptation remains unknown. This report described a function of BnRH6 in drought stress response. BnRH6 was sufficiently induced by osmotic stress. Transgenic Brassica napus and Arabidopsis thaliana (Arabidopsis) overexpressing BnRH6 (OE) showed a drought tolerance phenotype, characterized by improved plant growth, increased survival rates, reduced water loss, leaf chlorosis and oxidative stress. Furthermore, BnRH6 was also induced by exogenous abscisic acid (ABA). BnRH6 overexpression plants exhibited ABA hypersensitivity with lagging seed germination, growth stunt and diminished stomatal opening in the presence of ABA, suggesting the involvement of ABA signal. Assessment of several well-identified drought stress responsive genes such as Calcium-dependent Protein Kinase 14 (BnCDPK14), Enhanced Response to ABA1 (BnERA1) and ABA Insensitive 1 (BnABI1) revealed that their expressions were accordingly changed in BnOE plants, possibly with interplays between BnRH6 and those genes. Our data highlighted the functional role of BnRH6, which plays a positive role in active regulation of drought stress response likely through an ABA-dependent manner in rapeseed plants.