Exogenous application of glycine betaine facilitates yam tuber healing via positively regulating suberin deposition and energy status

Abstract

Suberin deposition at wound site severs as protective barrier accelerating fruit and vegetables healing. Studies have manifested that glycine betaine (GB) is able to enhance tolerance toward abiotic stresses in fruit and vegetables. However, knowledge on the function of GB on suberin deposition during yam tuber healing has not been revealed. In this study, yam tubers treated with GB had significantly lower malondialdehyde (MDA) content, electrolyte leakage (EL), weight loss (WL) and disease index (DI) compared to control tubers. GB treatment increased genes expression and activities of enzymes associated with suberin biosynthesis, such as phenylalanine ammonia lyase (DoPAL), cytochrome P450 fatty acid ω-hydroxylases (DoCYP86A1 and DoCYP94B3) and GDSL lipase/esterase proteins (DoGELP38, DoGELP51 and DoGELP96), resulting in monomers accumulation (including hydroxycinnamic acids, C20 fatty acid, ω-hydroxyacids and α, ω-diacids) and suberin deposition. Tubers treated with GB had higher activities of H⁺-ATPase, Ca²⁺-ATPase and cytochrome c oxidase (CCO), thereby maintaining higher energy status (ATP and ADP content, and energy charge (EC)). Furthermore, ATP content in GB group displayed positive correlations with suberin monomers accumulation. The results indicate that GB application is able to enhance suberin biosynthetic genes expression and enzymes activities and offer essential energy for suberin biosynthesis by improving energy status, eventually resulting in suberin deposition at wound sites for yam tuber healing.