Gagné-Bourque François, Mayer Boris F, Charron Jean-Benoit, Vali Hojatollah, Bertrand Annick, Jabaji Suha
Department of Plant Science, Macdonald Campus of McGill University, 21,111 Lakeshore Rd. Ste-Anne-de-Bellevue, Québec, CANADA, H9X 3V9.
Facility of Electron Microscopy Research (FEMR) McGill University, 3640 University Street, Montréal, Québec, CANADA, H3A 0C7.
PLoS One. 2015 Jun 23;10(6):e0130456. doi: 10.1371/journal.pone.0130456. eCollection 2015.
Plant growth-promoting bacteria (PGB) induce positive effects in plants, for instance, increased growth and reduced abiotic stresses susceptibility. The mechanisms by which these bacteria impact the host plant are numerous, diverse and often specific. Here, we studied the agronomical, molecular and biochemical effects of the endophytic PGB Bacillus subtilis B26 on the full life cycle of Brachypodium distachyon Bd21, an established model species for functional genomics in cereal crops and temperate grasses. Inoculation of Brachypodium with B. subtilis strain B26 increased root and shoot weights, accelerated growth rate and seed yield as compared to control plants. B. subtilis strain B26 efficiently colonized the plant and was recovered from roots, stems and blades as well as seeds of Brachypodium, indicating that the bacterium is able to migrate, spread systemically inside the plant, establish itself in the aerial plant tissues and organs, and is vertically transmitted to seeds. The presence of B. subtilis strain B26 in the seed led to systemic colonization of the next generation of Brachypodium plants. Inoculated Brachypodium seedlings and mature plants exposed to acute and chronic drought stress minimized the phenotypic effect of drought compared to plants not harbouring the bacterium. Protection from the inhibitory effects of drought by the bacterium was linked to upregulation of the drought-response genes, DREB2B-like, DHN3-like and LEA-14-A-like and modulation of the DNA methylation genes, MET1B-like, CMT3-like and DRM2-like, that regulate the process. Additionally, total soluble sugars and starch contents increased in stressed inoculated plants, a biochemical indication of drought tolerance. In conclusion, we show a single inoculation of Brachypodium with a PGB affected the whole growth cycle of the plant, accelerating its growth rates, shortening its vegetative period, and alleviating drought stress effects. These effects are relevant to grasses and cereal crops.
植物促生细菌（PGB）对植物具有积极影响，例如促进生长和降低对非生物胁迫的敏感性。这些细菌影响宿主植物的机制多种多样且往往具有特异性。在此，我们研究了内生植物促生细菌枯草芽孢杆菌B26对短柄草Bd21整个生命周期的农艺学、分子和生化影响，短柄草Bd21是谷类作物和温带禾本科植物功能基因组学的一个成熟模式物种。与对照植物相比，用枯草芽孢杆菌菌株B26接种短柄草可增加根和地上部重量，加快生长速率并提高种子产量。枯草芽孢杆菌菌株B26能有效定殖于植物，可从短柄草的根、茎、叶片以及种子中分离得到，这表明该细菌能够迁移，在植物体内系统传播，在地上部植物组织和器官中定殖，并垂直传递至种子。种子中存在枯草芽孢杆菌菌株B26导致下一代短柄草植物被系统定殖。与未携带该细菌的植物相比，接种枯草芽孢杆菌的短柄草幼苗和成熟植株在遭受急性和慢性干旱胁迫时，干旱的表型影响最小化。该细菌对干旱抑制作用的保护与干旱响应基因DREB2B-like、DHN3-like和LEA-14-A-like的上调以及调控该过程的DNA甲基化基因MET1B-like、CMT3-like和DRM2-like的调节有关。此外，受胁迫接种植物中总可溶性糖和淀粉含量增加，这是耐旱性的生化指标。总之，我们表明用一种植物促生细菌单次接种短柄草会影响植物的整个生长周期，加快其生长速率，缩短其营养期，并减轻干旱胁迫影响。这些影响与禾本科植物和谷类作物相关。
