Biochimie et Physiologie Moléculaire des Plantes, UMR Univ. Montpellier, CNRS, INRA, SupAgro, 34060, Montpellier Cedex 2, France.
Institut des Biomolécules Max Mousseron, UMR 5247, CNRS-UM-ENSCM, Faculté de Pharmacie, 15 Avenue Charles Flahault, BP 14491, F34093, Montpellier, Cedex 5, France.
Plant J. 2019 May;98(3):418-433. doi: 10.1111/tpj.14238. Epub 2019 Mar 12.
Root hairs, as lateral extensions of epidermal cells, provide large absorptive surfaces to the root and are major actors in plant hydromineral nutrition. In contact with the soil they also constitute a site of interactions between the plant and rhizospheric microorganisms. In legumes, initiation of symbiotic interactions with N -fixing rhizobia is often triggered at the root hair cell membrane in response to nodulation factors secreted by rhizobia, and involves early signaling events with changes in H , Ca , K and Cl fluxes inducing transient depolarization of the cell membrane. Here, we aimed to build a functional repertoire of the major root hair conductances to cations and anions in the sequenced legume model Medicago truncatula. Five root hair conductances were characterized through patch-clamp experiments on enzymatically recovered root hair protoplasts. These conductances displayed varying properties of voltage dependence, kinetics and ion selectivity. They consisted of hyperpolarization- and depolarization-activated conductances for K , cations or Cl . Among these, one weakly outwardly rectifying cationic conductance and one hyperpolarization-activated slowly inactivating anionic conductance were not known as active in root hairs. All five conductances were detected in apical regions of young growing root hairs using membrane spheroplasts obtained by laser-assisted cell-wall microdissection. Combined with recent root hair transcriptomes of M. truncatula, this functional repertoire of conductances is expected to help the identification of candidate genes for reverse genetics studies to investigate the possible role of each conductance in root hair growth and interaction with the biotic and abiotic environment.
根毛是表皮细胞的侧向延伸，为根提供了较大的吸收表面，是植物水矿营养的主要因素。与土壤接触时，它们也是植物与根际微生物相互作用的场所。在豆科植物中，与固氮根瘤菌的共生相互作用的启动通常是在根毛细胞膜上响应根瘤菌分泌的结瘤因子而触发的，涉及早期信号事件，导致 H 、Ca 、K 和 Cl 流的变化，从而诱导细胞膜的瞬时去极化。在这里，我们旨在构建已测序豆科模式植物蒺藜苜蓿中主要阳离子和阴离子根毛电导的功能目录。通过对酶回收的根毛原生质体进行膜片钳实验，鉴定了五种根毛电导。这些电导表现出不同的电压依赖性、动力学和离子选择性特征。它们由 K 、阳离子或 Cl 的超极化和去极化激活的电导组成。其中，一种弱的外向整流阳离子电导和一种超极化激活的缓慢失活的阴离子电导在根毛中并不活跃。在激光辅助细胞壁微切割获得的膜球形体上，在年轻生长的根毛的顶端区域检测到所有这五种电导。结合最近的蒺藜苜蓿根毛转录组，这种电导的功能目录有望有助于鉴定候选基因，用于反向遗传学研究，以研究每种电导在根毛生长和与生物及非生物环境相互作用中的可能作用。
