The breeding of new stenospermocarpic seedless grape cultivars is of particular importance to the growing table grape market and grape processing industry. However, the developmental and genetic architectures of soft‐seed and seedlessness traits are unclear. In this study, we performed anatomical, histochemical and gene expression analyses to characterize the morphological and genetic basis of the seed hardness of 'Hongju', a stenospermocarpic soft‐seed grape cultivar developed by crossbreeding maternal 'Italia' and paternal 'Perlon' cultivars. We found intensively lignified medium integument layers in the seeds of hard‐seed cultivars, but these layers were degraded in the stenospermocarpic seedless cultivars beginning 35 days after flowering. The expression of genes related to the lignin and cellulose biosynthesis pathways was downregulated, whereas that of several cell‐wall loosening‐related genes was upregulated in 'Hongju' compared with 'Italia' beginning at 21 days after flowering. These results suggest that transcriptional suppression of the lignin and cellulose biosynthesis pathways coupled with reduced formation of medium integument plays an important role in the development of soft seeds in stenospermocarpic seedless grape cultivars.

中文翻译：

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葡萄（Vitis vinifera cv）的解剖，生化和转录组分析。'红菊'揭示了有关硬皮果香软种子葡萄种子硬度的新信息

新的硬皮果无核葡萄品种的育种对成长中的鲜食葡萄市场和葡萄加工业特别重要。但是，软种子和无核性状的发育和遗传结构尚不清楚。在这项研究中，我们进行了解剖，组织化学和基因表达分析，以表征'Hongju'种子硬度的形态和遗传基础，该品种是由母本'Italia'和父本'Perlon'杂交育成的无胸果皮软种子葡萄品种。我们在硬种子品种的种子中发现了强化木质化的中间珠被层，但是这些层在花后35天开始的无胚果香的无核品种中被降解。木质素和纤维素生物合成途径相关基因的表达下调，而从开花后第21天开始，与“意大利”相比，“红菊”中几个与细胞壁松弛相关的基因的表达上调。这些结果表明，木质素和纤维素生物合成途径的转录抑制与中等覆盖层形成的减少相结合，在无角果核无核葡萄品种的软种子发育中起重要作用。