A Cassava Drought Inducible CC-Type Glutaredoxin, MeGRX232, Negatively Regulates Drought Tolerance In Arabidopsis By Inhibition Of ABA-Dependent Stoma

Abstract

CC-type glutaredoxins (GRXs) are a land plant-specific GRX subgroup that evolved from CGFS GRXs, and participate in organ development and stress responses through the regulation of transcription factors. Here, genome-wide analysis identified 18 CC-type GRXs in the cassava genome, of which six (MeGRX058, 232, 360, 496, 785, and 892) were induced by drought and ABA stress in cassava leaves. Furthermore, we found that overexpression of MeGRX232 results in drought hypersensitivity in soil-grown plants, with a higher water loss rate, but with increased tolerance of mannitol and ABA in Arabidopsis on the sealed agar plates. The ABA induced stomatal closure is impaired in MeGRX232-OE Arabidopsis. Further analysis reveals that the overexpression of MeGRX232 leads to more ROS accumulation in guard cells. MeGRX232 can interact with TGA5 from Arabidopsis and MeTGA074 from cassava in vitro and in vivo. The results of microarray assays show that MeGRX232-OE affected the expression of a set of drought and oxidative stress related genes. Taken together, we demonstrated that CC-type GRXs involved in ABA signal transduction and play roles in response to drought through regulating stomatal closure.\n\nNovelty statementWe found that drought and ABA stress induced the transcription of CC-type glutaredoxins (GRXs) in cassava leaves. Ectopic expression of one of them, MeGRX232 in Arabidopsis affected the sensitivity to abscisic acid (ABA) and mannitol, and caused drought hypersensitivity by impairment of ABA-dependent stomatal closure.