Abstract：
Phenylpropanoids, a class of specialized metabolites, play crucial roles in plant growth and stress adaptation and include diverse phenolic compounds such as flavonoids. Phenylalanine ammonia-lyase (PAL) and chalcone synthase (CHS) are essential enzymes functioning at the entry points of general phenylpropanoid biosynthesis and flavonoid biosynthesis, respectively. In Arabidopsis, PAL and CHS are turned over through ubiquitination-dependent proteasomal degradation. Specific kelch domain-containing F-Box (KFB) proteins as components of ubiquitin E3 ligase directly interact with PAL or CHS, leading to polyubiquitinated PAL and CHS, which in turn influences phenylpropanoid and flavonoid production. Although phenylpropanoids are vital for tomato nutritional value and stress responses, the post-translational regulation of PAL and CHS in tomato remains unknown. We identified 31 putative KFB-encoding genes in the tomato genome. Our homology analysis and phylogenetic study predicted four PAL-interacting SlKFBs, while SlKFB18 was identified as the sole candidate for the CHS-interacting KFB. Consistent with their homolog function, the predicted four PAL-interacting SlKFBs function in PAL degradation. Surprisingly, SlKFB18 did not interact with tomato CHS and the overexpression or knocking out of SlKFB18 did not affect phenylpropanoid contents in tomato transgenic lines, suggesting its irreverence with flavonoid metabolism. Our study successfully discovered the post-translational regulatory machinery of PALs in tomato while highlighting the limitation of relying solely on a homology-based approach to predict interacting partners of F-box proteins.
摘要：
苯丙烷类，一类特殊的代谢产物,在植物生长和胁迫适应中起关键作用，包括多种酚类化合物，如类黄酮。苯丙氨酸氨裂解酶（PAL）和查尔酮合成酶（CHS）是在一般苯丙素生物合成和类黄酮生物合成的切入点发挥作用的必需酶。分别。在拟南芥中,PAL和CHS通过泛素化依赖性蛋白酶体降解而被翻转。作为泛素E3连接酶的成分，含有特定kelch结构域的F-Box（KFB）蛋白直接与PAL或CHS相互作用，导致多泛素化PAL和CHS，进而影响苯丙素和类黄酮的生产。虽然苯丙素类对番茄的营养价值和应激反应至关重要，番茄中PAL和CHS的翻译后调节仍然未知。我们在番茄基因组中鉴定了31个推定的KFB编码基因。我们的同源性分析和系统发育研究预测了四个PAL相互作用的SlKFBs，而SlKFB18被确定为CHS相互作用KFB的唯一候选。与它们的同源功能一致，预测的四个与PAL相互作用的SlKFBs在PAL降解中的作用。令人惊讶的是,SlKFB18不与番茄CHS相互作用，并且SlKFB18的过表达或敲除不影响番茄转基因品系中的苯丙烷含量，表明它与类黄酮代谢无关。我们的研究成功地发现了番茄中PAL的翻译后调控机制，同时强调了仅依靠基于同源性的方法来预测F-box蛋白的相互作用伴侣的局限性。
