Zhu Sirui, Martínez Pacheco Javier, Estevez José M, Yu Feng
College of Biology, State Key Laboratory of Chemo/Biosensing and Chemometrics, Hunan Key Laboratory of Plant Functional Genomics and Developmental Regulation, Hunan University, Changsha, China.
Fundación Instituto Leloir and Instituto de Investigaciones Bioquímicas de Buenos Aires (IIBBA-CONICET), Av. Patricias Argentinas 435, Buenos Aires, CP C1405BWE, Argentina.
New Phytol. 2020 Jul;227(1):45-49. doi: 10.1111/nph.16497. Epub 2020 Mar 29.
Root hair (RH) size has vital physiological implications, since it influences the surface area of the root and thus the ability of the plant to absorb water and nutrients from the soil. Arabidopsis ROOT HAIR DEFECTIVE 6-LIKE 4 (RSL4), a bHLH transcription factor, controls the expression of hundreds of RH genes, and RSL4 expression itself can trigger ectopic RH growth. Recent studies reveal an autocrine mechanism governing plant RH cell growth in which the extracellular peptide RAPID ALKALINIZATION FACTOR 1 (RALF1) and receptor FERONIA (FER) act as a central hub between the cell surface and downstream signaling events. RALF1-FER promotes the phosphorylation of eIF4E1. Then, phosphorylated eIF4E1 further regulates the synthesis of RH proteins, including RSL4, to promote RH growth. High levels of RSL4 exert a negative feedback on RALF1 expression via directly binding to the RALF1 gene promoter, slowing RH growth and determining final RH cell size.
根毛（RH）大小具有重要的生理意义，因为它影响根的表面积，进而影响植物从土壤中吸收水分和养分的能力。拟南芥根毛缺陷6样4（RSL4）是一种bHLH转录因子，可控制数百个RH基因的表达，而RSL4自身的表达可引发异位根毛生长。最近的研究揭示了一种控制植物根毛细胞生长的自分泌机制，其中细胞外肽快速碱化因子1（RALF1）和受体FERONIA（FER）在细胞表面和下游信号事件之间起到核心枢纽作用。RALF1-FER促进eIF4E1的磷酸化。然后，磷酸化的eIF4E1进一步调节包括RSL4在内的根毛蛋白的合成，以促进根毛生长。高水平的RSL4通过直接结合RALF1基因启动子对RALF1表达产生负反馈，减缓根毛生长并决定最终的根毛细胞大小。
