Beneficial Bacteria Isolated from Grapevine Inner Tissues Shape <i>Arabidopsis thaliana</i> Roots

We investigated the potential plant growth-promoting traits of 377 culturable endophytic bacteria, isolated from Vitis vinifera cv. Glera, as good biofertilizer candidates in vineyard management. Endophyte ability in promoting plant growth was assessed in vitro by testing ammonia production, phosphate solubilization, indole-3-acetic acid (IAA) and IAA-like molecule biosynthesis, siderophore and lytic enzyme secretion. Many of the isolates were able to mobilize phosphate (33%), release ammonium (39%), secrete siderophores (38%) and a limited part of them synthetized IAA and IAA-like molecules (5%). Effects of each of the 377 grapevine beneficial bacteria on Arabidopsis thaliana root development were also analyzed to discern plant growth-promoting abilities (PGP) of the different strains, that often exhibit more than one PGP trait. A supervised model-based clustering analysis highlighted six different classes of PGP effects on root architecture. A. thaliana DR5::GUS plantlets, inoculated with IAA-producing endophytes, resulted in altered root growth and enhanced auxin response. Overall, the results indicate that the Glera PGP endospheric culturable microbiome could contribute, by structural root changes, to obtain water and nutrients increasing plant adaptation and survival. From the complete cultivable collection, twelve promising endophytes mainly belonging to the Bacillus but also to Micrococcus and Pantoea genera, were selected for further investigations in the grapevine host plants towards future application in sustainable management of vineyards.本研究针对从歌雷拉葡萄（Vitis vinifera cv. Glera）中分离得到的377株可培养内生细菌（endophytic bacteria）展开研究，评估其作为葡萄园管理中优良生物肥料候选菌株的植物促生潜力。通过体外（in vitro）实验检测氨产生、磷酸盐溶解、吲哚-3-乙酸（indole-3-acetic acid, IAA）及类IAA分子生物合成、铁载体（siderophore）与裂解酶分泌能力，以评估内生细菌的植物促生能力。结果显示，33%的分离菌株可活化磷酸盐、39%可释放铵离子、38%可分泌铁载体，仅5%的菌株能够合成IAA及类IAA分子。本研究还分析了全部377株葡萄有益细菌对拟南芥（Arabidopsis thaliana）根发育的影响，以解析不同菌株的植物促生（plant growth-promoting, PGP）能力——多数菌株往往兼具多种PGP性状。基于监督模型的聚类分析（supervised model-based clustering analysis）将菌株对根系构型的PGP效应划分为6个不同类别。接种产IAA内生细菌的拟南芥DR5::GUS幼苗，其根系生长发生改变且生长素响应增强。综上，本研究结果表明，歌雷拉葡萄内生可培养微生物组的PGP功能菌群可通过改变根系结构，提升植株对水分和养分的获取能力，进而增强植物适应性与存活率。从全部可培养菌株库中，筛选得到12株具有应用潜力的内生细菌，它们主要隶属于芽孢杆菌属（Bacillus），同时也包含微球菌属（Micrococcus）和泛菌属（Pantoea）菌株；后续将以葡萄为宿主开展进一步研究，以期未来应用于葡萄园可持续管理。