背景:转化酶(INVs)是糖代谢中的关键酶,蔗糖裂解成葡萄糖和果糖,在植物生长发育和逆境胁迫反应中起着重要作用,然而,西番莲中的INV基因家族尚未有系统报道。
结果:在这项研究中,从百香果基因组中鉴定出16个PeINV基因,并根据其亚细胞位置和染色体位置进行命名。这些包括六个细胞壁转化酶(CWINV)基因,两个液泡转化酶(VINV)基因,和8个中性/碱性转化酶(N/AINV)基因。基因结构,系统发育树,利用生物信息学方法预测了PeINV基因家族的顺式作用元件。结果表明,PeINV基因的上游启动子区含有各种反应元件;特别是,PeVINV2、PeN/AINV3、PeN/AINV5、PeN/AINV6、PeN/AINV7和PeN/AINV8有较多的反响元件。此外,不同非生物胁迫下PeINV基因的表达谱(干旱,盐,寒冷的温度,和高温)表明PeCWINV5,PeCWINV6,PeVINV1,PeVINV2,PeN/AINV2,PeN/AINV3,PeN/AINV6和PeN/AINV7对这些非生物胁迫具有显着的响应,这与顺式作用元素预测结果一致。蔗糖,葡萄糖,和果糖是百香果果肉中的主要可溶性成分。总可溶性糖的含量,己糖,甜度指数在果实成熟早期显著增加。转录组数据表明,随着果实发育和成熟度的增加,PeCWINV2、PeCWINV5和PeN/AINV3的表达水平呈上调趋势,特别是对于显示最高丰度的PeCWINV5,这与可溶性糖的积累和甜度指数有关。瞬时过表达结果表明,果糖的含量,过表达PeCWINV5的果实果肉中葡萄糖和蔗糖增加。据推测,这种细胞壁转化酶基因,PeCWINV5可能在蔗糖卸载和己糖积累中起重要作用。
结论:在这项研究中,我们首次系统地鉴定了百香果中的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,我们筛选出参与己糖积累的关键候选基因。本研究为进一步研究INV基因奠定了基础,有利于西番莲的遗传改良育种。
BACKGROUND: 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.
RESULTS: 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.
CONCLUSIONS: 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.