Water-deficit tolerance in citrus is mediated by the down regulation of PIP gene expression in the roots

Abstract

Water deficit (WD) is a growing problem in agriculture. In citrus crops, genetically-determined rootstock characteristics are important factors influencing plant responses to WD. Aquaporins are involved in regulating the water supply to the plant by mediating water flow through the cell membranes. Recent studies support a direct role for aquaporins in plant water relations and demonstrate their involvement in WD tolerance. This study investigates the relationship between photosynthetic and water-balance parameters with aquaporin expression levels and hydraulic conductance of roots (Kr) in conditions of moderate WD in citrus rootstocks. The plant materials used were the rootstocks Poncirus trifoliata (L.) Raf. (PT), Cleopatra mandarin (Citrus reshni Hort ex Tan.) (CM) and 030115 (a hybrid of the two former rootstocks), all grafted with the citrus variety 'Valencia Late' (C. sinensis (L.) Osb). Plants were irrigated with two differents irrigation doses (normal irrigation and moderate WD) during 70 days and leaf water potential (ψs), net CO 2 assimilation (A CO2 ), transpiration, stomatal conductance (gs) and substomatal CO 2 concentration (Ci) were measured periodically under both irrigation conditions. Kr and PIP1 and PIP2 gene expression levels in fine roots of control plants and plants subjected to WD on day 43 of the experiment were determined. Under WD conditions, the hybrid 030115 drastically reduced aquaporin expression and Kr, accompanied by a loss of plant vigour but without reducing the net CO 2 assimilation (A CO2 ). PT maintained the same aquaporin expression level and similar Kr under WD as under normal irrigation conditions, but suffered a sharp reduction in A CO2 . CM, which has lower Kr and aquaporin expression than PT under both normal irrigation conditions and WD, responded better to water stress conditions than PT. Low aquaporin levels, or down-regulated aquaporin Plant Soil (2011) 347:91-104 expression, accompanied by decreased plant vigour led to decreased plasma membrane permeability, thereby facilitating water retention in the cells under water stress conditions. This may induce water stress tolerance in citrus rootstocks.

Enhanced root hydraulic conductance by aquaporin regulation accounts for silicon alleviated salt-induced osmotic stress in Sorghum bicolor L

“…8, under short-term salt stress, the transcriptional levels of SbPIP1;6, SbPIP2;2, and SbPIP2;6 were upregulated by Si. Previous studies have shown either decreases or increases in aquaporin activity under stress conditions in different plants (Hachez et al, 2012;Vandeleur et al, 2009;Rodriguez-Gamir et al, 2011). Our result was consistent with previous studies showing that the upregulation of aquaporin aids salt resistance (Qian et al, 2014).…”

Rootstock Breeding for Abiotic Stress Tolerance in Citrus

“…Treeby et al [78] investigated irrigation management and rootstock effects on navel orange and reported that irrigation management is far more critical for external fruit quality for trees on sweet orange and, to a lesser extent, trees on the citranges compared to trees on trifoliate orange and Cleopatra mandarin.…”

Genome-Wide Characterization and Expression Analysis of Major Intrinsic Proteins during Abiotic and Biotic Stresses in Sweet Orange (Citrus sinensis L. Osb.)

“…reshni Hort exTan.) and one of their hybrids, subjected to moderate water deficit [ 21 ], and in roots of P . trifoliata , Cleopatra mandarin and Carrizo citrange ( C .…”