Biotechnology of Natural Products, Technische Universität München, Liesel-Beckmann-Str. 1, 85354, Freising, Germany.
Department of Food and Agricultural Product Technology, Faculty of Agricultural Technology, Universitas Gadjah Mada, Jl. Flora No. 1 - Bulaksumur, Yogyakarta, Indonesia.
Plant J. 2019 Dec;100(6):1237-1253. doi: 10.1111/tpj.14512. Epub 2019 Oct 8.
Fruit softening in Fragaria (strawberry) is proposed to be associated with the modification of cell wall components such as xyloglucan by the action of cell wall-modifying enzymes. This study focuses on the in vitro and in vivo characterization of two recombinant xyloglucan endotransglucosylase/hydrolases (XTHs) from Fragaria vesca, FvXTH9 and FvXTH6. Mining of the publicly available F. vesca genome sequence yielded 28 putative XTH genes. FvXTH9 showed the highest expression level of all FvXTHs in a fruit transcriptome data set and was selected with the closely related FvXTH6 for further analysis. To investigate their role in fruit ripening in more detail, the coding sequences of FvXTH9 and FvXTH6 were cloned into the vector pYES2 and expressed in Saccharomyces cerevisiae. FvXTH9 and FvXTH6 displayed xyloglucan endotransglucosylase (XET) activity towards various acceptor substrates using xyloglucan as the donor substrate. Interestingly, FvXTH9 showed activity of mixed-linkage glucan:xyloglucan endotransglucosylase (MXE) and cellulose:xyloglucan endotransglucosylase (CXE). The optimum pH of both FvXTH9 and FvXTH6 was 6.5. The prediction of subcellular localization suggested localization to the secretory pathway, which was confirmed by localization studies in Nicotiana tabacum. Overexpression showed that Fragaria × ananassa fruits infiltrated with FvXTH9 and FvXTH6 ripened faster and showed decreased firmness compared with the empty vector control pBI121. Thus FvXTH9 and also FvXTH6 might promote strawberry fruit ripening by the modification of cell wall components.
草莓果实软化被认为与细胞壁成分（如木葡聚糖）的修饰有关，这种修饰是通过细胞壁修饰酶的作用实现的。本研究聚焦于两个来自草莓（ Fragaria vesca ）的重组木葡聚糖内转糖基酶/水解酶（XTH）的体外和体内特性，它们是 FvXTH9 和 FvXTH6 。对公开可用的 F. vesca 基因组序列进行挖掘，得到了 28 个推定的 XTH 基因。在果实转录组数据集的所有 FvXTH 中，FvXTH9 的表达水平最高，因此选择与它密切相关的 FvXTH6 进行进一步分析。为了更详细地研究它们在果实成熟中的作用，将 FvXTH9 和 FvXTH6 的编码序列克隆到载体 pYES2 中，并在酿酒酵母中表达。FvXTH9 和 FvXTH6 用木葡聚糖作为供体底物，对各种受体底物表现出木葡聚糖内转糖基酶（XET）活性。有趣的是，FvXTH9 还表现出混合链葡聚糖：木葡聚糖内转糖基酶（MXE）和纤维素：木葡聚糖内转糖基酶（CXE）的活性。FvXTH9 和 FvXTH6 的最适 pH 值均为 6.5 。亚细胞定位的预测表明它们定位于分泌途径，这一预测通过在烟草中的定位研究得到了证实。过表达表明，与空载体对照 pBI121 相比，草莓（ Fragaria × ananassa ）果实中浸润了 FvXTH9 和 FvXTH6 的果实成熟更快，硬度降低。因此，FvXTH9 以及 FvXTH6 可能通过细胞壁成分的修饰来促进草莓果实的成熟。
