Jiménez-Vázquez Kirán Rubí, López-Bucio Jesús Salvador, Ruíz-Herrera León Francisco, López-Bucio José
Instituto de Investigaciones Químico-Biológicas, Universidad Michoacana de San Nicolás de Hidalgo, Edificio B3, Ciudad Universitaria, C.P. 58030, Morelia, Michoacán, México.
CONACYT-Instituto de Investigaciones Químico-Biológicas, Universidad Michoacana de San Nicolas de Hidalgo, Edificio B1, Ciudad Universitaria, C.P. 58030, Morelia, Michoacán, México.
Plant J. 2025 May;122(4):e70226. doi: 10.1111/tpj.70226.
The root cap protects the meristem as the root grows and senses stimuli such as gravity and nutrient availability. Although it enables tight interaction with the rhizosphere, a role in perceiving microorganisms is unknown. Here, through Arabidopsis direct root inoculation with the plant growth promoting rhizobacterium Achromobacter sp. 5B1, we unveiled a critical, opposite role of two transcription factors, FEZ and SOMBRERO, in mediating growth, waving, and coiling of primary roots as a response to the bacterium. In Arabidopsis seedlings with mutations in FEZ, the rhizobacterium had increased formation of coils, whereas in seedlings harboring mutations in SOMBRERO, the formation of coils did not occur and the root maintains normal gravity response. This correlated with the elongation of the cells on the right or convex side, an aspect that is increased in fez-2 mutants but does not manifest itself in smb-3 mutants. Interaction with Achromobacter sp. 5B1 increased the size of the root cap, which coincided with decreased or increased detection in vivo of FEZ:FEZ:GFP and SMB:SMB:GFP, respectively, and with the phenotype of smb-3 mutants, which develop roots with a huge cap irrespective of bacterization. Expression of auxin transporters PIN1, PIN2, PIN3, PIN4, and PIN7 overall decreased in the WT, fez-2, and smb-3 upon bacterial inoculation, suggesting that the agravitropic behavior of roots may be linked to disturbance of auxin distribution within the root tip. Our data indicate that the root cap senses the rhizobacterium Achromobacter sp. 5B1 through FEZ and SOMBRERO for the directional growth and soil exploration.
根冠在根生长时保护分生组织，并感知重力和养分有效性等刺激。尽管它能与根际紧密相互作用，但在感知微生物方面的作用尚不清楚。在这里，通过用促进植物生长的根际细菌无色杆菌属5B1直接接种拟南芥的根，我们揭示了两个转录因子FEZ和SOMBRERO在介导主根生长、弯曲和盘绕以响应该细菌方面的关键且相反的作用。在FEZ发生突变的拟南芥幼苗中，根际细菌增加了盘绕的形成，而在SOMBRERO发生突变的幼苗中，盘绕未形成且根保持正常的重力反应。这与右侧或凸侧细胞的伸长相关，这一现象在fez - 2突变体中增加，但在smb - 3突变体中不明显。与无色杆菌属5B1的相互作用增加了根冠的大小，这分别与体内检测到的FEZ:FEZ:GFP减少或增加以及SMB:SMB:GFP减少或增加一致，并且与smb - 3突变体的表型一致，无论是否接种细菌，该突变体都发育出具有巨大根冠的根。接种细菌后，野生型、fez - 2和smb - 3中生长素转运蛋白PIN1、PIN2、PIN3、PIN4和PIN7的表达总体下降，这表明根的无重力行为可能与根尖内生长素分布的紊乱有关。我们的数据表明，根冠通过FEZ和SOMBRERO感知根际细菌无色杆菌属5B1，以实现定向生长和土壤探索。
