Switchgrass (Panicum virgatum L.) is an important perennial, noninvasive, tall ornamental grass that adds color and texture to gardens and landscapes. Moreover, switchgrass has been considered a forage and bioenergy crop because of its vigorous growth, low-input requirements, and broad geography. Here, we identified PvWOX3a from switchgrass, which encodes a WUSCHEL-related homeobox transcription factor. Transgenic overexpression of PvWOX3a in switchgrass increased stem length, internode diameter, and leaf blade length and width, all of which contributed to a 95% average increase in dry weight biomass compared with control plants. Yeast one-hybrid and transient dual-luciferase assays showed that PvWOX3a can repress the expression of gibberellin 2-oxidase and cytokinin oxidase/dehydrogenase through apparently direct interaction with their promoter sequences. These results suggested that overexpression of PvWOX3a could increase gibberellin and cytokinin levels in transgenic switchgrass plants, which promotes cell division, elongation, and vascular bundle development. We also overexpressed PvWOX3a in a transgenic miR156-overexpressing switchgrass line that characteristically exhibited more tillers, thinner internodes, and narrower leaf blades. Double transgenic switchgrass plants displayed significant increases in internode length and diameter, leaf blade width, and plant height but retained a tiller number comparable to that of plants expressing miR156 alone. Ultimately, the double transgenic switchgrass plants produced 174% more dry-weight biomass and 162% more solubilized sugars on average than control plants. These findings indicated that PvWOX3a is a viable potential genetic target for engineering improved shoot architecture and biomass yield of horticulture, fodder, and biofuel crops.

中文翻译：

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PvWOX3a在柳枝稷中的过表达促进茎发育并增加株高

柳枝稷 (穗花L.) 是一种重要的多年生、非侵入性、高大的观赏草，可为花园和景观增添色彩和质感。此外，柳枝稷因其生长旺盛、投入要求低和地域广阔而被认为是一种饲料和生物能源作物。在这里，我们确定了PvWOX3a来自柳枝稷，它编码了一个与 WUSCHEL 相关的同源框转录因子。转基因过表达PvWOX3a柳枝稷增加了茎长、节间直径和叶片长度和宽度，与对照植物相比，所有这些都导致干重生物量平均增加 95%。酵母单杂交和瞬时双荧光素酶测定表明 PvWOX3a 可以抑制赤霉素2-氧化酶和细胞分裂素氧化酶/脱氢酶通过与它们的启动子序列明显的直接相互作用。这些结果表明，过表达PvWOX3a可以增加转基因柳枝稷植物中赤霉素和细胞分裂素的水平，从而促进细胞分裂、伸长和维管束发育。我们也过度表达PvWOX3a在转基因 miR156 过表达柳枝稷株系中，该株系特征性地表现出更多的分蘖、更薄的节间和更窄的叶片。双转基因柳枝稷植物在节间长度和直径、叶片宽度和株高方面表现出显着增加，但保留了与单独表达 miR156 的植物相当的分蘖数。最终，与对照植物相比，双转基因柳枝稷植物产生的干重生物量增加了 174%，溶解的糖量增加了 162%。这些发现表明PvWOX3a是一个可行的潜在遗传目标，用于工程改良园艺、饲料和生物燃料作物的枝条结构和生物量产量。