Characterization and differential expression of ethylene receptor genes during fruit development and dehiscence of durian (Durio zibethinus)

Durian (Durio zibethinus) is a climacteric fruit. Biochemical changes take place in the durian pulp while the husk is dehiscent during fruit ripening. Fruit development of durian cv. Monthong showed a sigmoid curve and reached a maturity stage week 16 after anthesis, while fruit dehiscence started a week after harvest, was hastened by ethephon treatment, and delayed by 1-methylcyclopropene (1-MCP). 1-MCP treatment delayed dehiscence for 5 days from day 7 to day 12 compared with control fruit at 25 degrees C. Two ethylene receptors (DzETR1 and DzETR2), a CTR1-like protein (DzCTR1) and two ethylene insensitive-like proteins (DzEIL1 and DzEIL2) in the pulp and husk shared high homology to Theobroma cacao. The transcript levels of DzETR2, DzCTR1 and DzEIL2 slightly decreased during fruit development (week 2 to week 10), while DzETR2 transcript level showed the highest expression. The gene expression of DzETR2 in the dehiscence zone, increased at day 12 after harvest, while gene expression of DzETR1, DzCTR1 and DzEIL2 slightly increased after harvest. All genes were reduced in expression with 1-MCP treatment. After that, an increase in expression was found at day 9, followed by a gradual decrease until day 12. These results suggest that DzETR2 plays a role in fruit development and dehiscence of ripening durian.