Biology subjects

Very, A.-A.

Publications and source records attributed to Very, A.-A..

2 recordsLinked to original sources

bioRxiv2019

The Medicago truncatula HKT family: Ion transport properties and regulation of expression upon abiotic stresses and symbiosis

Soil salinity is one of the most important abiotic stresses affecting plant growth. In legumes, symbiotic nitrogen fixation in nodules is affected by salt stress, and salinity tolerance is variable among species. Genes from the High affinity K+ Transporter (HKT) family are known to play crucial roles in salt stress tolerance in different plant species. In legumes these transporters are still very poorly characterized.. Here we study the HKT transporter family from the model legume Medicago trunacatula, which is moderately tolerant to salinity. The genome of this species comprises five HKT genes, hereafter named MtHKT1;1 to MtHKT1;5. Phylogenetic analysis indicated that the MtHKT polypeptides belong to HKT subfamily 1. Three members (MtHKT1;2, MtHKT1;4 and MtHKT1;5) of the Medicago truncatula family were cloned and expressed in Xenopus oocytes. Their electrophysiological properties revealed a permeability 10 times higher for Na+ than for K+ and varying rectification properties. Expression analyses of the three MtHKT genes under different biotic and abiotic conditions suggested that MtHKT1;5 is the main transporter from this family in the root, the three genes sharing a decrease of expression in drought and salt stress conditions in non inoculated plants as well as plants inoculated with rhizobia. In the shoot, the three MtHKT would be present at similar levels independently on the applied stresses. Based on biomass and ion content analysis, the nodule appeared as the most sensitive organ to the applied salt and drought stresses. The level of expression of the three MtHKT genes was strongly decreased by both stresses in the nodule.

plant biology↗

bioRxiv2019

Medicago truncatula possesses a single Shaker outward K+ channel: functional characterization and roles in planta

The model legume Medicago truncatula possesses a single outward Shaker K+ channel, while Arabidopsis thaliana possesses two channels of this type, named SKOR and GORK, the former having been shown to play a major role in K+ secretion into the xylem sap in the root vasculature and the latter to mediate the efflux of K+ across the guard cell membrane upon stomatal closure. Here we show that the expression pattern of the single M. truncatula outward Shaker channel, which has been named MtGORK, includes the root vasculature, guard cells and root hairs. As shown by patch-clamp experiments on root hair protoplasts, besides the Shaker-type slowly-activating outwardly-rectifying K+ conductance encoded by MtGORK, a second K+-permeable conductance, displaying fast activation and weak rectification, can be expressed by M. truncatula. A KO mutation resulting in absence of MtGORK activity is shown to weakly reduce K+ translocation to shoots, and only in plants engaged in rhizobial symbiosis, but to strongly affect the control of stomatal aperture and transpitational water loss. In legumes, the early electrical signaling pathway triggered by Nod Factor perception is known to comprise a short transient depolarization of the root hair plasma membrane. In absence of MtGORK functional expression, while the rate of the membrane repolarization is shown to be decreased by about 3 times, this defect is without any consequence on infection thread development and nodule production, indicating that the plant capacity to engage rhizobial symbiosis does not require integrity of the early electrical signaling events.

plant biology↗