Figure legends
Figure 1 . Images of a mature leaf (a ), the 2nd fruit trusses (b ) and the root (c ) from representative plants of tomato cv Sugar Drop grafted onto the WT AC (SD/AC) and the NCED OE lines SP12 (SD/SP12) and SP5 (SD/SP5) grown under 3.5 dS m–1 (equivalent to 35 mM NaCl) for 100 days under greenhouse conditions.
Figure 2 . Variation of net photosynthesis rate (AN ) after 130, 163 and 180 DST of tomato cv. Sugar Drop grafted onto the WT AC (SD/AC) and the NCED OE lines SP12 (SD/SP12) and SP5 (SD/SP5) grown under 3.5 dS m–1(equivalent to 35 mM NaCl) (a ). Net photosynthesis (AN ), stomatal conductance (gs ) and intrinsic water use efficiency (WUEi) of tomato cv. Sugar Drop grafted onto the WT AC (SD/AC) and the NCED OE lines SP12 (SD/SP12) and SP5 (SD/SP5) grown under 3.5 dS m–1 for 180 days under greenhouse conditions. Different letters indicate significant differences between graft combination (n =3, P ≤ 0.05) (b ). Scanning electron micrograph (SEM) of transverse sectioning of tomato leaf (300x) showing the differences in epidermis and mesophyll layers between cv. Sugar Drop grafted onto the WT AC (SD/AC) and the NCED OE line SP12 (SD/SP12) grown under 3.5 dS m–1 for 180 days under greenhouse conditions (c ). Substomatal CO2(Ci ) of cv. Sugar Drop grafted onto the WT AC (SD/AC) and the NCED OE lines SP12 (SD/SP12) and SP5 (SD/SP5) grown under 3.5 dS m–1 for 180 days under greenhouse conditions (d ). SEM visualization (330x) of adaxial (left) and abaxial (right) leaf surfaces of cv Sugar Drop grafted onto WT AC (SD/AC) and the NCED OE line SP12 (SD/SP12) grown under 3.5 dS m–1 for 180 days under greenhouse conditions (e ).
Figure 3 . Abscisic acid (ABA) concentrations in mature fruit juice (180 DST), mature, green and flower truss xylem sap (180 DST), leaf (130 DST), leaf phloem (180 DST), leaf xylem sap (130 DST), root xylem sap (200 DST) and root (200 DST) of tomato cv Sugar Drop grafted onto the WT AC (SD/AC) and the NCED OE lines SP12 (SD/SP12) and SP5 (SD/SP5) grown under a 3.5 dS m–1 (equivalent to 35 mM NaCl) under greenhouse conditions. Different letters indicate significant differences between genotypes (n =3, P ≤0.05) (a ). Dihydrophaseic acid (DPA) and phaseic acid (PA) concentrations in leaf (130 DST), root xylem sap (200 DST) and root (200 DST) of tomato cv Sugar Drop grafted onto the WT AC (SD/AC) and the NCED OE line SP12 (SD/SP12) grown under 3.5 dS m–1 under greenhouse conditions (b ). * indicate statistically significant difference between graft combinations (n=3, P ≤ 0.05).
Figure 4 . HeatMap of the variation of trans -zeatin (t -Z), isopentenyl adenine (iP), 1-aminocyclopropane-1-carboxylic acid (ACC), indole-3-acetic acid (IAA), gibberellin A3 (GA3), jasmonic acid (JA) and salicylic acid (SA) concentrations in mature fruit juice (180 DST), mature truss xylem sap (180 DST), green fruit juice (180 DST) green fruit xylem sap (180 DST), flower truss xylem sap (180 DST), leaf (130 DST), leaf phloem (180 DST), leaf xylem sap (130 DST), root xylem sap (200 DST) and root (200 DST) of tomato cv Sugar Drop grafted onto the WT AC (SD/AC) and the NCED OE lines SP12 (SD/SP12) and SP5 (SD/SP5) grown under 3.5 dS m–1 (equivalent to 35 mM NaCl) under greenhouse conditions. -1 and -2 indicate significant decrease at P ≤ 0.05 and P ≤ 0.01, respectively; 0 indicates not significant effects and +1 and +2 indicate significant increase at P ≤ 0.05 andP ≤ 0.01, respectively. ND, not detected.
Figure 5 . Venn diagram showing the intersection of the differentially expressed genes identified in roots (a ) and upregulated and downregulated genes in roots of SD/SP5 against SD/AC, SD/SP12 against SD/AC and SD/SP5 + SD/SP12 against SD/AC grown under 3.5 dS m–1 (equivalent to 35 mM NaCl) for 200 days under greenhouse conditions (b ).
Figure 6 . ABA (a ) stress (b ) and aquaporin (c ) related genes differentially expressed in root tissues comparing plants of SD/SP12 and SD/SP5 against SD/AC in response to 3.5 dS m–1 (equivalent to 35 mM NaCl) for 200 days under greenhouse conditions. Real time PCR quantification (RT-qPCR) of some ABA-related selected genes is also given.
Figure 7 . Cytokinin (CK)(a ), gibberellin (GA) (b ), jasmonic acid (JA)(c ), ethylene (d ) and auxin (e ) related genes differentially expressed in root tissues comparing plants of SD/SP12 and SD/SP5 against SD/AC in response to 3.5 dS m–1(equivalent to 35 mM NaCl) for 200 days under greenhouse conditions. Real time PCR quantification (RT-qPCR) of some ABA-related selected genes is also given.
Figure 8 . Proposed model to explain the performance of ABA overproducing rootstocks under salinity conditions. The improved growth and yield phenotype of the plants grafted onto NCED OE rootstocks can be explained through local (root) and systemic (scion) responses mediated by root-to-shoot communication. (a ) At local level in the root, ABA overproduction seems to interfere with stress mediated response by decreasing root expression of ABA receptors (PYLs) and signalling components (WRKYs ), thus altering sensitivity to ABA. The reduced ABA sensitivity in the roots appear to diminish auxin activity (ARFs, auxin transport from the shoot) and increase ethylene-related processes (ERFs, ACCs ) leading to reduced RSA (mainly lateral roots). Inhibited IPT gene supports diminished CK synthesis in the rootstock and t -Z transport to the shoot. (b ) At the systemic level in the scion, although root-to-shoot ABA signal has not been detected, a higher transport to the shoot cannot be ruled out (increased NCED expression and ABA catabolites). The increased foliar iP accumulation and phloem transport (in response to reduced t -Z transport from the roots) along with transitory increase of ABA and JA in leaf tissue seems to modify leaf growth and mesophyll structure leading to improved photosynthesis (AN) activity. Moreover, the induced xylem GA3 in growing fruits seems to enhance reproductive growth. Improved photosynthesis and reduced root growth lead to optimized source-sink relations in benefit of scion development and yield. Arrow and bar heads indicate positive and negative regulation, respectively.