MAIN CONCLUSION EgPHI-1 is a member of PHI-1/EXO/EXL protein family. Its overexpression in tobacco resulted in changes in biomass partitioning, xylem fiber length, secondary cell wall thickening and composition, and lignification. Here, we report the functional characterization of a PHOSPHATE-INDUCED PROTEIN 1 homologue showing differential expression in xylem cells from Eucalyptus species of contrasting phenotypes for wood quality and growth traits. Our results indicated that this gene is a member of the PHI-1/EXO/EXL family. Analysis of the promoter cis-acting regulatory elements and expression responses to different treatments revealed that the Eucalyptus globulus PHI-1 (EgPHI-1) is transcriptionally regulated by auxin, cytokinin, wounding and drought. EgPHI-1 overexpression in transgenic tobacco changed the partitioning of biomass, favoring its allocation to shoots in detriment of roots. The stem of the transgenic plants showed longer xylem fibers and reduced cellulose content, while the leaf xylem had enhanced secondary cell wall thickness. UV microspectrophotometry of individual cell wall layers of fibers and vessels has shown that the transgenic plants exhibit differences in the lignification of S2 layer in both cell types. Taken together, the results suggest that EgPHI-1 mediates the elongation of secondary xylem fibers, secondary cell wall thickening and composition, and lignification, making it an attractive target for biotechnological applications in forestry and biofuel crops.

中文翻译：

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EgPHI-1 是来自蓝桉的磷酸诱导-1 基因，参与芽生长、木质部纤维长度和次生细胞壁特性


主要结论EgPHI-1是PHI-1/EXO/EXL蛋白家族的成员。它在烟草中的过度表达导致生物量分配、木质部纤维长度、次生细胞壁增厚和组成以及木质化的变化。在这里，我们报告了磷酸诱导蛋白 1 同源物的功能表征，该同源物显示在木材质量和生长性状对比表型的桉树物种的木质部细胞中存在差异表达。我们的结果表明该基因是 PHI-1/EXO/EXL 家族的成员。对启动子顺式作用调控元件和对不同处理的表达反应的分析表明，蓝桉PHI-1（EgPHI-1）的转录受到生长素、细胞分裂素、创伤和干旱的调控。 EgPHI-1在转基因烟草中的过度表达改变了生物量的分配，有利于其分配到芽而不利于根。转基因植物的茎显示出更长的木质部纤维和降低的纤维素含量，而叶木质部具有增加的次生细胞壁厚度。纤维和血管的各个细胞壁层的紫外显微分光光度测定表明，转基因植物在两种细胞类型中的 S2 层木质化方面表现出差异。综上所述，结果表明 EgPHI-1 介导次生木质部纤维的伸长、次生细胞壁的增厚和组成以及木质化，使其成为林业和生物燃料作物中生物技术应用的有吸引力的目标。