Laboratorio de Fisiología Vegetal y Genética Molecular, Instituto de Biología Vegetal y Biotecnología, Universidad de Talca, Casilla 747, Talca, Chile.
Plant Sci. 2010 Nov;179(5):479-88. doi: 10.1016/j.plantsci.2010.07.018. Epub 2010 Aug 3.
Chilean strawberry (Fragaria chiloensis), the maternal progenitor of Fragaria×ananassa, has emerged as a new berry fruit with excellent organoleptic characteristics. The fast softening of strawberries is a limiting step for their commercialization. Fruit softening has been shown to be related to cell wall degradation. Several enzymatic activities related to this process have been isolated in strawberry fruit, however xyloglucan endotransglycosylase/hydrolase (XTH) enzymes have not been identified or characterized so far. Two XTH genes were identified in an EST database of F. chiloensis fruit with high homology to other plant XTHs. We isolated the full-length cDNAs associated to these ESTs in F. chiloensis (Fc-XTH1, Fc-XTH2). Phylogenetic analysis suggests that both F. chiloensis XTH genes belong to distant phylogenetic groups of XTHs. Moreover, DNA gel-blot analysis indicates different genomic organization between the two genes. By means of Real Time qPCR analysis, gene expression profiles show a transcriptional profile of Fc-XTH1 transcripts congruent with a probable role during strawberry ripening, while that exhibited by Fc-XTH2 could be related with vegetative processes like leaf growth. On the other hand, immunodetection and enzyme activity assays allow the detection of XTH-related proteins and high xyloglucan transglycosylating (XETA) and degrading (XDA) activities at the turning stage. The data presented confirms the existence of two divergent XTH genes, and XET and XEH activities, in F. chiloensis fruit.
智利草莓（ Fragaria chiloensis ）是草莓（ Fragaria ×ananassa ）的母本，已成为一种具有优良感官特性的新型浆果。草莓的快速软化是其商业化的一个限制步骤。草莓果实软化与细胞壁降解有关。已经分离出几种与该过程相关的酶活性，但到目前为止尚未鉴定或表征木葡聚糖内转糖基酶/水解酶（ XTH ）酶。在智利草莓果实的 EST 数据库中，鉴定出两个与其他植物 XTH 高度同源的 XTH 基因。我们在智利草莓中分离出与这些 EST 相关的全长 cDNA （ Fc-XTH1 ， Fc-XTH2 ）。系统发育分析表明，这两个智利草莓 XTH 基因属于 XTH 基因的远缘进化群。此外，DNA 凝胶印迹分析表明这两个基因在基因组组织上存在差异。通过实时 qPCR 分析，基因表达谱显示 Fc-XTH1 转录本的转录谱与草莓成熟过程中的可能作用一致，而 Fc-XTH2 转录本的表达可能与叶片生长等营养过程有关。另一方面，免疫检测和酶活性测定允许检测到与 XTH 相关的蛋白质，并且在转折阶段检测到高木葡聚糖转糖基（ XETA ）和降解（ XDA ）活性。所提供的数据证实了在智利草莓果实中存在两个不同的 XTH 基因和 XET 和 XEH 活性。
