Non-adapted bacterial infection suppresses plant reproduction

Environmental stressors, including pathogens, substantially
affect the growth of host plants. However, how non-adapted
bacteria influence nonhost plants has not been
reported. Here, we reveal that infection of Arabidopsis
flowers by Xanthomonas oryzae pv.
oryzae PXO99A, a bacterial pathogen causing rice blight disease,
suppresses ovule initiation and reduces seed number without causing
visible disease symptoms. TleB, secreted by the type VI secretion system
(T6SS), interacts with plant E3 ligase PUB14,
and disrupts the function of the PUB14-BZR1 module,
leading to decreased ovule initiation and seed yield. In the other site,
PUB14 concurrently promotes TleB’s degradation. Our
findings indicate that bacterial infections in nonhost plants directly
repress offspring production. The regulatory mechanism by
effectors-PUB14-BZR1 is widely present, suggesting that plants may
balance reproduction and
defense and produce fewer offspring to conserve
resources, thus enabling them to remain in a standby mode prepared for
enhanced resistance.

包括病原菌在内的环境胁迫因子，可显著影响寄主植物的生长发育。然而，非适应性细菌对非寄主植物的影响机制尚未见报道。本研究发现，导致水稻白叶枯病的细菌性病原菌——稻黄单胞菌稻致病变种（Xanthomonas oryzae pv. oryzae）PXO99A侵染拟南芥（Arabidopsis）花器官后，虽未引发可见病害症状，却可抑制胚珠起始过程并降低结籽数。由VI型分泌系统（T6SS）分泌的效应蛋白TleB，可与植物E3泛素连接酶（E3 ligase）PUB14相互作用，破坏PUB14-BZR1信号模块的功能，进而导致胚珠起始效率下降、种子产量降低。与此同时，PUB14还可促进TleB的降解。本研究结果表明，非寄主植物中的细菌侵染会直接抑制后代产量。效应因子-PUB14-BZR1调控通路广泛存在，这提示植物或可平衡生殖与防御过程：通过减少后代产生以节约资源，使自身维持在可快速增强抗性的待机状态。