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Overproduction of ABA in rootstocks alleviates salinity stress in tomato shoots
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  • Cristina Martínez Andújar,
  • Ascensión Martínez-Pérez,
  • Alfonso Albacete Moreno,
  • Purificación A Martínez-Melgarejo,
  • Ian Dodd,
  • Andrew J. Thompson,
  • Almudena Ferrández-Ayela,
  • Jose Manuel Perez-Perez,
  • Miriam Gifford,
  • Francisco P,rez Alfocea
Cristina Martínez Andújar
Centro de Edafología y Biología Aplicada del Segura
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Ascensión Martínez-Pérez
Centro de Edafología y Biología Aplicada del Segura
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Alfonso Albacete Moreno
Centro de Edafología y Biología Aplicada del Segura
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Purificación A Martínez-Melgarejo
Centro de Edafologia y Biologia Aplicada del Segura
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Ian Dodd
University of Lancaster
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Andrew J. Thompson
Cranfield University
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Almudena Ferrández-Ayela
Universidad Miguel Hernández
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Jose Manuel Perez-Perez
Universidad Miguel Hernandez
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Miriam Gifford
School of Life Sciences and Warwick Integrative Synthetic Biology Centre
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Francisco P,rez Alfocea
Centro de Edafología y Biología Aplicada del Segura
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Abstract

To determine whether root-supplied ABA alleviates saline stress, tomato (Solanum lycopersicum L. cv. Sugar Drop) was grafted onto two independent lines overexpressing the SlNCED1 (9-cis-epoxycarotenoid dioxygenase) gene (NCED OE) and wild type rootstocks. After 200 days of salinity irrigation (EC = 3.5 dS m-1), plants with NCED OE rootstocks had 30% higher fruit yield, but root biomass and lateral root development was reduced. Although NCED OE rootstocks upregulated ABA-signalling (AREB, ATHB12), ethylene-related (ACCs, ERFs), aquaporin (PIPs) and stress-related (TAS14, KIN, LEA) genes, downregulation of PYL ABA receptors and signalling components (WRKYs), ethylene synthesis (ACOs) and auxin responsive factors occurred. Elevated SlNCED1 expression enhanced ABA levels in reproductive tissue while ABA catabolites accumulated in leaf and xylem sap suggesting homeostatic mechanisms. NCED OE also reduced xylem cytokinin transport to the shoot and stimulated foliar 2-isopentenyl adenine (iP) accumulation and phloem transport. Moreover, increased xylem gibberellin GA3 levels in growing fruit trusses was associated with enhanced reproductive growth. Improved photosynthesis without changes in stomatal conductance was consistent with hormone-mediated alteration of leaf growth and mesophyll structure, which combined with lower assimilate requirement in the roots and systemic changes in hormone balances could explain enhanced vigour, reproductive growth and yield under saline stress.