A CSE-containing promoter region of AcoINV3 is associated with 15℃-induced pineapple translucency during fruit enlargement

Abstract

Abstract Background Pineapple is the third most widely cultivated tropical fruit globally and the fourth in China. Annual losses due to translucency account for approximately 20% of China’s pineapple production. Studying its mechanism and developing controlling strategies is important for the industry. Chilling during fruit enlargement often leads to severe translucency, and larger fruits tend to show higher incidence of translucency. However, the underlying mechanisms remain unclear. Results 15℃ treatment during fruit enlargement increased apoplastic fructose and glucose levels and up-regulated expression of the cell wall invertase gene AcoINV3 . The fructose and glucose content in pulp intercellular space of AcoINV3 mutant MU-2 is significantly less than that of the pineapple transformed with the empty vector. These values of MU-2 treated with 15 ℃ were similar with those of MU-2 always grown in 25℃ greenhouse. Under 15℃-stress, MU-2 exhibited significantly lower translucency rates than empty-vector control. Its single-fruit weight was also much less than the control. A cold shock element (CSE, 5′-CCGAC-3′) in the AcoINV3 promoter was identified as a 15℃-responsive cis -element. The AcoINV3 CSE-knockout line CSE-3 exhibited a significantly lower incidence of translucency than wild-type plants when subjected to 15℃ during fruit enlargement. Its single-fruit weight was comparable to that of wild-type plants under 25℃ conditions. Conclusions These results suggest that 15℃ treatment during fruit enlargement induces translucency and promotes fruit weight. This inducement was associated with the CSE in the AcoINV3 promoter. The CSE in the AcoINV3 promoter has 15℃-responsive function. Targeted knockout of the CSE reduces translucency incidence without compromising single-fruit weight under 15℃ condition.