Apoplastic barriers, aquaporin gene expression and root and cell hydraulic conductivity in phosphate‐limited sheepgrass plants

Abstract

Mineral nutrient supply can affect the hydraulic property of roots. The aim of the present work on sheepgrass (Leymus chinensis L.) plants was to test whether any changes in root hydraulic conductivity (Lp; exudation analyses) in response to a growth‐limiting supply of phosphate (P) are accompanied by changes in (1) cell Lp via measuring the cell pressure, (2) the aquaporin (AQP) gene expression by performing qPCR and (3) the formation of apoplastic barriers, by analyzing suberin lamella and Casparian bands via cross‐sectional analyses in roots. Plants were grown hydroponically on complete nutrient solution, containing 250 µM P, until they were 31–36 days old, and then kept for 2–3 weeks on either complete solution, or transferred on solution containing 2.5 µM (low‐P) or no added P (no‐P). Phosphate treatments caused significant decreases in root and cell‐Lp and AQP gene expression, while the formation of apoplastic barriers increased, particularly in lateral roots. Experiments using the AQP inhibitor mercury (Hg) suggested that a significant portion of radial root water uptake in sheepgrass occurs along a path involving AQPs, and that the Lp of this path is reduced under low‐ and no‐P. It is concluded that a growth‐limiting supply of phosphate causes parallel changes in (1) cell Lp and aquaporin gene expression (decrease) and (2) apoplastic barrier formation (increase), and that the two may combine to reduce root Lp. The reduction in root Lp, in turn, facilitates an increased root‐to‐shoot surface area ratio, which allocates resources to the root, sourcing the limiting nutrient.

The Effect of Trichoderma citrinoviride Treatment under Salinity Combined to Rhizoctonia solani Infection in Strawberry (Fragaria x ananassa Duch.)

“…In agreement with our results, Paranidharan et al [72] found increased POX activities in rice in response to infection by Rhizoctonia solani. According to these results, we can speculate that increased lignin synthesis during both salt stress and pathogen infection in order to establish an apoplastic barrier and to make the cell wall less permeable to water loss might also be the case in our study [73]. On the other hand, POX activity of the all Trichoderma-treated plants under stress was lower than that of the control levels.…”

Phosphate-Dependent Regulation of Growth and Stresses Management in Plants

“…The regulation of aquaporins membrane (localized at the plasma membrane) that control water movement within/out of the plants and influence the hydraulic property of roots are affected. The expression of aquaporin genes coding for protein membranes responsible for apoplastic barriers synthesis decreased (Li et al, 2020). Specifically, the genes encoding the 3-Pi dehydrogenase bound synthesis LcPIP1;1, LcPIP2;1, LcPIP2;4, HvPIP2;2, and HvPIP2;5 decreased.…”

“…A recent study has highlighted new candidate genes expressed during exposure of plants to combined Pi starvation and drought stresses (Armand et al, 2019;Li et al, 2020). The regulation of aquaporins membrane (localized at the plasma membrane) that control water movement within/out of the plants and influence the hydraulic property of roots are affected.…”

Interrelations of nutrient and water transporters in plants under abiotic stress

“…Also, P starvation could cause combined changes in root Lp and aquaporins gene expression together with the formation of endodermal apoplastic barriers in roots (Li et al 2019a). In fact, recently, Li et al (2019a, b, c) showed a decrease in the gene expression of six PIPs aquaporins ( LcPIP1;1 , LcPIP1;4 , LcPIP2;1 , LcPIP2;4 , Put‐LcPIP2;2 and Put‐LcPIP2;5 ) in Leymus chinesis L. under low P availability. Indeed, P starvation may also modulate aquaporins activity, due to changes in their phosphorylation status (Wang et al 2016).…”