Overexpression of GsCNGC20-f from Glycine soja confers submergence tolerance to hairy-root composite soybean plants and Arabidopsis seedlings by enhancing anaerobic respiration

Cyclic nucleotide-gated channels (CNGCs) in plants are nonselective Ca2+-permeable cationic channel proteins, that are part of the signal transduction cascade system and are involved in the physiological regulation of plant responses to adverse environments. This study firstly showed that the stronger submergence tolerance of G. soja P18B seedlings compared to the G. max cultivar KF1, might be related to the enhanced processes of Ca2+ signal cascade (higher Ca2+ content), anaerobic metabolism (higher activities of PDC and ADH), and energy reserves (higher ATP level) in the leaves during submergence. Then, the potential submergence-responsive differentially expressed genes (DEGs) enriched in voltage-gated potassium channel activity, such as GsCNGC20-f and GsCNGC20-g, and those enriched in calcium ion binding, i.e. GsCaML, GsCAM4, GsCML41, and GsCML45 were identified through leaf transcriptomic analysis of P18B and KF1 under submergence. The qRT-PCR, tobacco leaf transient expression and GUS staining displayed a more obviously induced upregulation of GsCNGC20-f and GsCNGC20-g by submergence stress. BiFC and Y2H assays showed that plasma membrane-located GsCNGC-f could interact with GsCaM4 or GsCaML. Finally, overexpression of GsCNGC20-f could alleviate submergence injury in hairy-root composite soybean plants or transgenic Arabidopsis seedlings by maintaining a higher content of Ca2+ and activities of PDC and ADH (associated with upregulated gene expression of PDCs and ADHs), and thereafter enhancing ATP levels in the leaves via improved anaerobic respiration under hypoxic conditions. The functions of GsCNGC20-f involving in the adaptation and survival of G. soja P18B seedlings under submergence stress can provide new perspectives for the molecular breeding of flooding-tolerant soybeans or other crops.