Tropical Crops Genetic Resources Institute, National Key Laboratory for Tropical Crop Breeding / Key Laboratory of Crop Gene Resources and Germplasm Enhancement in Southern China, Ministry of Agriculture and Rual Affairs / Key Laboratory of Tropical Crops Germplasm Resources Genetic Improvement and Innovation of Hainan Province / Germplasm Repository of Passiflora, Chinese Academy of Tropical Agricultural Sciences, Haikou, Hainan, 571101, P.R. China.
Guangxi Crop Genetic Improvement and Biotechnology Laboratory, Key Laboratory of Passion fruit Biology and Genetic Breeding, Ministry of Agriculture and Rural Affairs, Guangxi Academy of Agricultural Sciences, Nanning, Guangxi, 530007, P.R. China.
BMC Plant Biol. 2024 Sep 6;24(1):836. doi: 10.1186/s12870-024-05392-y.
Invertases (INVs) are key enzymes in sugar metabolism, cleaving sucrose into glucose and fructose and playing an important role in plant development and the stress response, however, the INV gene family in passion fruit has not been systematically reported.
In this study, a total of 16 PeINV genes were identified from the passion fruit genome and named according to their subcellular location and chromosome position. These include six cell wall invertase (CWINV) genes, two vacuolar invertase (VINV) genes, and eight neutral/alkaline invertase (N/AINV) genes. The gene structures, phylogenetic tree, and cis-acting elements of PeINV gene family were predicted using bioinformatics methods. Results showed that the upstream promoter region of the PeINV genes contained various response elements; particularly, PeVINV2, PeN/AINV3, PeN/AINV5, PeN/AINV6, PeN/AINV7, and PeN/AINV8 had more response elements. Additionally, the expression profiles of PeINV genes under different abiotic stresses (drought, salt, cold temperature, and high temperature) indicated that PeCWINV5, PeCWINV6, PeVINV1, PeVINV2, PeN/AINV2, PeN/AINV3, PeN/AINV6, and PeN/AINV7 responded significantly to these abiotic stresses, which was consistent with cis-acting element prediction results. Sucrose, glucose, and fructose are main soluble components in passion fruit pulp. The contents of total soluble sugar, hexoses, and sweetness index increased significantly at early stages during fruit ripening. Transcriptome data showed that with an increase in fruit development and maturity, the expression levels of PeCWINV2, PeCWINV5, and PeN/AINV3 exhibited an up-regulated trend, especially for PeCWINV5 which showed highest abundance, this correlated with the accumulation of soluble sugar and sweetness index. Transient overexpression results demonstrated that the contents of fructose, glucose and sucrose increased in the pulp of PeCWINV5 overexpressing fruit. It is speculated that this cell wall invertase gene, PeCWINV5, may play an important role in sucrose unloading and hexose accumulation.
In this study, we systematically identified INV genes in passion fruit for the first time and further investigated their physicochemical properties, evolution, and expression patterns. Furthermore, we screened out a key candidate gene involved in hexose accumulation. This study lays a foundation for further study on INV genes and will be beneficial on the genetic improvement of passion fruit breeding.
转化酶（INV）是糖代谢的关键酶，能将蔗糖分解为葡萄糖和果糖，在植物发育和胁迫响应中发挥重要作用，但西番莲INV 基因家族尚未得到系统报道。
本研究从西番莲基因组中鉴定出 16 个 PeINV 基因，并根据其亚细胞定位和染色体位置进行命名。这些基因包括 6 个细胞壁转化酶（CWINV）基因、2 个液泡转化酶（VINV）基因和 8 个中性/碱性转化酶（N/AINV）基因。利用生物信息学方法预测了 PeINV 基因家族的基因结构、系统发育树和顺式作用元件。结果表明，PeINV 基因上游启动子区域含有各种响应元件；特别是 PeVINV2、PeN/AINV3、PeN/AINV5、PeN/AINV6、PeN/AINV7 和 PeN/AINV8 具有更多的响应元件。此外，不同非生物胁迫（干旱、盐、低温和高温）下 PeINV 基因的表达谱表明，PeCWINV5、PeCWINV6、PeVINV1、PeVINV2、PeN/AINV2、PeN/AINV3、PeN/AINV6 和 PeN/AINV7 对这些非生物胁迫有显著响应，这与顺式作用元件预测结果一致。蔗糖、葡萄糖和果糖是西番莲果肉中的主要可溶性成分。在果实成熟过程中，总可溶性糖、己糖和甜度指数在早期显著增加。转录组数据显示，随着果实发育和成熟的增加，PeCWINV2、PeCWINV5 和 PeN/AINV3 的表达水平呈上调趋势，尤其是 PeCWINV5 的表达量最高，这与可溶性糖和甜度指数的积累有关。瞬时过表达结果表明，在过表达 PeCWINV5 的果实果肉中，果糖、葡萄糖和蔗糖的含量增加。推测该细胞壁转化酶基因 PeCWINV5 可能在蔗糖卸载和己糖积累中发挥重要作用。
本研究首次系统鉴定了西番莲的 INV 基因，并进一步研究了它们的理化性质、进化和表达模式。此外，筛选出一个与己糖积累相关的关键候选基因。本研究为进一步研究 INV 基因奠定了基础，将有利于西番莲遗传改良和品种选育。
