Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana, USA.
Department of Plant Pathology and Crop Physiology, Louisiana State University Agricultural Center, Baton Rouge, Louisiana, USA.
Mol Plant Pathol. 2023 Nov;24(11):1400-1413. doi: 10.1111/mpp.13376. Epub 2023 Jul 10.
Bacterial panicle blight is caused by Burkholderia glumae and results in damage to rice crops worldwide. Virulence of B. glumae requires quorum sensing (QS)-dependent synthesis and export of toxoflavin, responsible for much of the damage to rice. The DedA family is a conserved membrane protein family found in all bacterial species. B. glumae possesses a member of the DedA family, named DbcA, which we previously showed is required for toxoflavin secretion and virulence in a rice model of infection. B. glumae secretes oxalic acid as a "common good" in a QS-dependent manner to combat toxic alkalinization of the growth medium during the stationary phase. Here, we show that B. glumae ΔdbcA fails to secrete oxalic acid, leading to alkaline toxicity and sensitivity to divalent cations, suggesting a role for DbcA in oxalic acid secretion. B. glumae ΔdbcA accumulated less acyl-homoserine lactone (AHL) QS signalling molecules as the bacteria entered the stationary phase, probably due to nonenzymatic inactivation of AHL at alkaline pH. Transcription of toxoflavin and oxalic acid operons was down-regulated in ΔdbcA. Alteration of the proton motive force with sodium bicarbonate also reduced oxalic acid secretion and expression of QS-dependent genes. Overall, the data show that DbcA is required for oxalic acid secretion in a proton motive force-dependent manner, which is critical for QS of B. glumae. Moreover, this study supports the idea that sodium bicarbonate may serve as a chemical for treatment of bacterial panicle blight.
细菌性穗枯病是由恶臭假单胞菌引起的，会对全球的水稻作物造成损害。恶臭假单胞菌的毒力需要群体感应（QS）依赖的毒黄素合成和输出，这是导致水稻受损的主要原因。DedA 家族是一种保守的膜蛋白家族，存在于所有细菌物种中。恶臭假单胞菌拥有 DedA 家族的一个成员，名为 DbcA，我们之前的研究表明，DbcA 对于毒黄素的分泌和在水稻感染模型中的毒力是必需的。恶臭假单胞菌以 QS 依赖的方式分泌草酸作为“共同利益”，以对抗静止期生长培养基中的毒性碱化。在这里，我们表明，B. glumaeΔdbcA 无法分泌草酸，导致碱性毒性和对二价阳离子的敏感性，这表明 DbcA 在草酸分泌中起作用。B. glumaeΔdbcA 在进入静止期时积累的酰基高丝氨酸内酯（AHL）QS 信号分子较少，可能是由于 AHL 在碱性 pH 下的非酶失活。ΔdbcA 中转录的毒黄素和草酸操纵子的表达下调。用碳酸氢钠改变质子动力也会减少草酸的分泌和 QS 依赖基因的表达。总的来说，这些数据表明，DbcA 以质子动力依赖的方式被需要用于草酸的分泌，这对于恶臭假单胞菌的 QS 至关重要。此外，这项研究支持了碳酸氢钠可以作为治疗细菌性穗枯病的化学物质的观点。
