Chlorophyll degradation is an important physiological process and is essential for plant growth and development. However, how chlorophyll degradation is controlled at the cellular and molecular level remains largely elusive. Pectin is a main component of the primary cell wall, and polygalacturonases (PGs) is a group of pectin-hydrolases that cleaves the pectin backbone and release oligogalacturonide. Whether and how PGs affect chlorophyll degradation metabolism and its association with ethylene (ETH) have not been reported before. Here, we report a novel function of PG in a mutant ‘high chlorophyll content1’ hcc1, which displayed a decrease in growth and yield. Our morphological, biochemical and genetic analyses of hcc1, knockout lines and complementation lines confirm the function of HCC1 in chlorophyll degradation. In hcc1, the PG activity, ETH content and D-galacturonic acid (D-GA) was significantly decreased and showed an increase in the thickness of the cell wall. Exogenous application of ETH and D-GA can increase ETH content and induce the expression of HCC1, which further can successfully induce the chlorophyll degradation in hcc1. Together, our data demonstrated a novel function of HCC1 in chlorophyll degradation via the ETH pathway.

叶绿素降解是一个重要的生理过程，对于植物的生长发育至关重要。然而，如何在细胞和分子水平上控制叶绿素降解仍然很大程度上难以捉摸。果胶是初生细胞壁的主要成分，多聚半乳糖醛酸酶（PG）是一组果胶水解酶，可裂解果胶骨架并释放寡聚半乳糖醛酸。 PGs是否以及如何影响叶绿素降解代谢及其与乙烯（ETH）的关联此前尚未有报道。在这里，我们报告了 PG 在突变体“高叶绿素含量 1”hcc1中的新功能，该突变体表现出生长和产量的下降。我们对hcc1 、敲除系和互补系的形态学、生化和遗传分析证实了HCC1在叶绿素降解中的功能。在hcc1中，PG活性、ETH含量和D-半乳糖醛酸(D-GA)显着降低，并且细胞壁厚度增加。外源施用ETH和D-GA可以增加ETH含量并诱导HCC1的表达，进而成功诱导hcc1中叶绿素的降解。总之，我们的数据证明了HCC1通过 ETH 途径降解叶绿素的新功能。