Shtern Amit, Keren-Keiserman Alexandra, Mauxion Jean-Philippe, Furumizu Chihiro, Alvarez John Paul, Amsellem Ziva, Gil Naama, Motenko Etel, Alkalai-Tuvia Sharon, Fallik Elazar, Gonzalez Nathalie, Goldshmidt Alexander
Institute of Plant Sciences, Agricultural Reserch Organization, Volcani Institute, HaMaccabbim Road 68, Rishon LeZion 7505101, Israel.
UMR1332 Biologie du fruit et Pathologie, INRAE, University of Bordeaux, F33882 Villenave d'Ornon, France.
J Exp Bot. 2023 Feb 5;74(3):848-863. doi: 10.1093/jxb/erac454.
The pericarp is the predominant tissue determining the structural characteristics of most fruits. However, the molecular and genetic mechanisms controlling pericarp development remain only partially understood. Previous studies have identified that CLASS-II KNOX genes regulate fruit size, shape, and maturation in Arabidopsis thaliana and Solanum lycopersicum. Here we characterized the roles of the S. lycopersicum CLASS-II KNOX (TKN-II) genes in pericarp development via a detailed histological, anatomical, and karyotypical analysis of TKN-II gene clade mRNA-knockdown (35S:amiR-TKN-II) fruits. We identify that 35S:amiR-TKN-II pericarps contain more cells around their equatorial perimeter and fewer cell layers than the control. In addition, the cell sizes but not the ploidy levels of these pericarps were dramatically reduced. Further, we demonstrate that fruit shape and pericarp layer number phenotypes of the 35S:amiR-TKN-II fruits can be overridden by the procera mutant, known to induce a constitutive response to the plant hormone gibberellin. However, neither the procera mutation nor exogenous gibberellin application can fully rescue the reduced pericarp width and cell size phenotype of 35S:amiR-TKN-II pericarps. Our findings establish that TKN-II genes regulate tomato fruit anatomy, acting via gibberellin to control fruit shape but utilizing a gibberellin-independent pathway to control the size of pericarp cells.
果皮是决定大多数果实结构特征的主要组织。然而，控制果皮发育的分子和遗传机制仍未完全清楚。先前的研究已经确定，II类KNOX基因调控拟南芥和番茄的果实大小、形状和成熟过程。在这里，我们通过对TKN-II基因分支mRNA敲低（35S:amiR-TKN-II）果实进行详细的组织学、解剖学和核型分析，来表征番茄II类KNOX（TKN-II）基因在果皮发育中的作用。我们发现，与对照相比，35S:amiR-TKN-II果实的果皮在赤道周长周围含有更多的细胞，细胞层数更少。此外，这些果皮的细胞大小显著减小，但倍性水平没有变化。进一步地，我们证明，已知能诱导对植物激素赤霉素产生组成型反应的procera突变体，可以掩盖35S:amiR-TKN-II果实的果形和果皮层数表型。然而，procera突变和外源赤霉素处理都不能完全挽救35S:amiR-TKN-II果皮减少的宽度和细胞大小表型。我们的研究结果表明，TKN-II基因通过赤霉素调控番茄果实解剖结构，控制果实形状，但利用一条不依赖赤霉素的途径来控制果皮细胞大小。
