College of Horticulture, Northwest A&F University, Taicheng Road NO.3, Yangling, Shaanxi Province, China.
State Key Laboratory of Crop Stress Biology for Arid Areas, Northwest A&F University, Taicheng Road NO.3, Yangling, Shaanxi Province, China.
BMC Plant Biol. 2021 Oct 13;21(1):469. doi: 10.1186/s12870-021-03220-1.
Decrease in anthocyanin content results in the loss of red color in leaves, petals and receptacles during development. The content of anthocyanin was affected by the biosynthesis and degradation of anthocyanin. Compared with the known detailed mechanism of anthocyanin biosynthesis, the degradation mechanism is not fully investigated. It is vital to study the degradation mechanism of anthocyanin in pear for promoting the accumulation of anthocyanin and inhibiting the red fading in pear.
Here, we reported that laccase encoded by PbLAC4-like was associated with anthocyanin degradation in pear. The expression pattern of PbLAC4-like was negatively correlated with the content of anthocyanin during the color fading process of pear leaves, petals and receptacles. Phylogenetic analysis and sequence alignment revealed that PbLAC4-like played a vital role in anthocyanin degradation. Thus, the degradation of anthocyanin induced by PbLAC4-like was further verified by transient assays and prokaryotic expression. More than 80% of anthocyanin compounds were degraded by transiently over-expressed PbLAC4-like in pear fruitlet peel. The activity of crude enzyme to degrade anthocyanin in leaves at different stages was basically consistent with the expression of PbLAC4-like. The anthocyanin degradation ability of prokaryotic induced PbLAC4-like protein was also verified by enzyme activity assay. Besides, we also identified PbMYB26 as a positive regulator of PbLAC4-like. Yeast one-hybrid and dual luciferase assay results showed that PbMYB26 activated PbLAC4-like expression by directly binding to the PbLAC4-like promoter.
Taken together, the PbLAC4-like activated by PbMYB26, was involved in the degradation of anthocyanin, resulting in the redness fading in different pear tissues.
在发育过程中，花色素苷含量的减少会导致叶片、花瓣和托片中的红色消失。花色素苷的含量受花色素苷生物合成和降解的影响。与已知的花色素苷生物合成详细机制相比，其降解机制尚未完全研究。研究梨中花色素苷的降解机制对于促进花色素苷的积累和抑制梨的红色褪色至关重要。
在这里，我们报道了由 PbLAC4-like 编码的漆酶与梨中花色素苷的降解有关。在梨叶片、花瓣和托片中花色褪色过程中，PbLAC4-like 的表达模式与花色素苷含量呈负相关。系统发育分析和序列比对表明，PbLAC4-like 在花色素苷降解中起重要作用。因此，通过瞬时测定和原核表达进一步验证了 PbLAC4-like 诱导的花色素苷降解。瞬时过表达 PbLAC4-like 可使梨幼果果皮中超过 80%的花色素苷化合物降解。不同发育阶段叶片中粗酶降解花色素苷的活性与 PbLAC4-like 的表达基本一致。通过酶活性测定还验证了原核诱导 PbLAC4-like 蛋白的花色素苷降解能力。此外，我们还鉴定了 PbMYB26 是 PbLAC4-like 的正调控因子。酵母单杂交和双荧光素酶测定结果表明，PbMYB26 通过直接结合 PbLAC4-like 启动子激活 PbLAC4-like 的表达。
综上所述，PbMYB26 激活的 PbLAC4-like 参与了花色素苷的降解，导致不同梨组织的红色褪色。
