Plant organ size and shape are major agronomic traits that depend on cell division and expansion, which are both regulated by complex gene networks. In several eudicot species belonging to the rosid clade, organ growth is controlled by a repressor complex consisting of PEAPOD (PPD) and KINASE-INDUCIBLE DOMAIN INTERACTING (KIX) proteins. The role of these proteins in asterids, which together with the rosids constitute most of the core eudicot species, is unknown. We used Clustered Regularly Interspaced Short Palindromic Repeats–CRISPR-associated protein 9 genome editing to target SlKIX8 and SlKIX9 in the asterid model species tomato (Solanum lycopersicum) and analyzed loss-of-function phenotypes. Loss-of-function of SlKIX8 and SlKIX9 led to the production of enlarged, dome-shaped leaves and these leaves exhibited increased expression of putative Solanum lycopersicum PPD (SlPPD target genes. Unexpectedly, kix8 kix9 mutants carried enlarged fruits with increased pericarp thickness due to cell expansion. At the molecular level, protein interaction assays indicated that SlKIX8 and SlKIX9 act as adaptors between the SlPPD and SlTOPLESS co-repressor proteins. Our results show that KIX8 and KIX9 are regulators of organ growth in asterids and can be used in strategies to improve important traits in produce such as thickness of the fruit flesh.

中文翻译：

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SlKIX8 和 SlKIX9 是番茄叶片和果实生长的负调控因子

植物器官的大小和形状是依赖于细胞分裂和扩张的主要农艺性状，它们都受到复杂基因网络的调控。在属于蔷薇进化枝的几种真双子叶植物中，器官生长由由 PEAPOD (PPD) 和激酶诱导域相互作用 (KIX) 蛋白组成的抑制复合物控制。这些蛋白质在小行星中的作用是未知的，小行星与玫瑰一起构成了大多数核心真双子叶植物物种。我们使用聚集规则间隔短回文重复序列–CRISPR 相关蛋白 9 基因组编辑来靶向小行星模型物种番茄（Solanum lycopersicum）中的 SlKIX8 和 SlKIX9，并分析功能丧失表型。SlKIX8 和 SlKIX9 的功能丧失导致生产扩大，蛋白质相互作用测定表明，SlKIX8 和 SlKIX9 作为 SlPPD 和 SlTOPLESS 共阻遏蛋白之间的衔接子。我们的研究结果表明，KIX8 和 KIX9 是小行星器官生长的调节剂，可用于改善果肉厚度等重要农产品性状的策略。蛋白质相互作用测定表明，SlKIX8 和 SlKIX9 作为 SlPPD 和 SlTOPLESS 共阻遏蛋白之间的衔接子。我们的研究结果表明，KIX8 和 KIX9 是小行星器官生长的调节剂，可用于改善果肉厚度等重要农产品性状的策略。