SummaryTomato (Solanum lycopersicum) stands as one of the most valuable vegetable crops globally, and fruit firmness significantly impacts storage and transportation. To identify genes governing tomato firmness, we scrutinized the firmness of 266 accessions from core collections. Our study pinpointed an ethylene receptor gene, SlEIN4, located on chromosome 4 through a genome‐wide association study (GWAS) of fruit firmness in the 266 tomato core accessions. A single‐nucleotide polymorphism (SNP) (A → G) of SlEIN4 distinguished lower (AA) and higher (GG) fruit firmness genotypes. Through experiments, we observed that overexpression of SlEIN4AA significantly delayed tomato fruit ripening and dramatically reduced fruit firmness at the red ripe stage compared with the control. Conversely, gene editing of SlEIN4AA with CRISPR/Cas9 notably accelerated fruit ripening and significantly increased fruit firmness at the red ripe stage compared with the control. Further investigations revealed that fruit firmness is associated with alterations in the microstructure of the fruit pericarp. Additionally, SlEIN4AA positively regulates pectinase activity. The transient transformation assay verified that the SNP (A → G) on SlEIN4 caused different genetic effects, as overexpression of SlEIN4GG increased fruit firmness. Moreover, SlEIN4 exerts a negative regulatory role in tomato ripening by impacting ethylene evolution through the abundant expression of ethylene pathway regulatory genes. This study presents the first evidence of the role of ethylene receptor genes in regulating fruit firmness. These significant findings will facilitate the effective utilization of firmness and ripening traits in tomato improvement, offering promising opportunities for enhancing tomato storage and transportation capabilities.

中文翻译：

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通过果实果皮微观结构探讨EIN4单核苷酸突变对番茄果实硬度多样性的影响

摘要番茄 (番茄）是全球最有价值的蔬菜作物之一，果实的硬度显着影响储存和运输。为了确定控制番茄硬度的基因，我们仔细检查了核心种质中 266 个种质的硬度。我们的研究查明了乙烯受体基因，SEIIN4，通过全基因组关联研究位于 4 号染色体上（全基因组关联分析) 266 个番茄核心种质的果实硬度。单核苷酸多态性 (SNP) (A → G)SEIIN4区分较低（AA）和更高的（GG）果实硬度基因型。通过实验，我们观察到过表达SEIIN4AA与对照相比，番茄果实成熟显着延迟，红熟期果实硬度显着降低。相反，基因编辑SEIIN4AA和基因编辑技术与对照相比，/Cas9显着加速了果实成熟，并显着提高了红熟阶段的果实硬度。进一步的研究表明，果实硬度与果皮微观结构的改变有关。此外，SEIIN4AA积极调节果胶酶活性。瞬时转化实验验证了 SNP (A → G)SEIIN4引起不同的遗传效应，因为过度表达SEIIN4GG增加果实硬度。而且，SEIIN4通过乙烯途径调控基因的丰富表达影响乙烯进化，从而在番茄成熟中发挥负调控作用。这项研究首次证明了乙烯受体基因在调节果实硬度中的作用。这些重大发现将有助于在番茄改良中有效利用硬度和成熟性状，为提高番茄储存和运输能力提供有希望的机会。