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ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Molecular Plant Pathology Laboratory » Research » Publications at this Location » Publication #303472
Title: Hormonal and metabolic regulation of tomato fruit sink activity and yield under salinity

Author
item ALBACETE, ALFONSO - Centro De Edafologia Y Biologia Aplicada Del Segura (CEBAS)
item CANTERO-NAVARRO, ELENA - Centro De Edafologia Y Biologia Aplicada Del Segura (CEBAS)
item BALIBREA, MARIA - Centro De Edafologia Y Biologia Aplicada Del Segura (CEBAS)
item MARTINEZ-ANDUJAR, CRISTINA - Centro De Edafologia Y Biologia Aplicada Del Segura (CEBAS)
item Smigocki, Anna
item ROITSCH, THOMAS - Centro De Edafologia Y Biologia Aplicada Del Segura (CEBAS)
item PEREZ-ALFOCEA, FRANCISCO - Centro De Edafologia Y Biologia Aplicada Del Segura (CEBAS)

Submitted to: Journal of Experimental Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/24/2014
Publication Date: 8/28/2014
Citation: Albacete, A., Cantero-Navarro, E., Balibrea, M.E., Martinez-Andujar, C., Smigocki, A.C., Roitsch, T., Perez-Alfocea, F. 2014. Hormonal and metabolic regulation of tomato fruit sink activity and yield under salinity. Journal of Experimental Botany. DOI: 10.1093/jxb/eru347.

Interpretive Summary: Salt contamination of soil and ground water reduces tomato yields. In the presence of salt, leaf death is enhanced and fruit growth decreases. Growth promoting plant hormones (cytokinins), known to enhance growth and disease resistance, and the activity of sugar building enzymes are reduced in the presence of salt. The combined effect of increasing cytokinin concentration and sucrose building enzymes was shown to reverse negative salt effects. We demonstrate that when cytokinin is applied to plants grown under salt stress conditions, the salt effect is reversed and tomato fruit number and weight increase. The enhanced growth is accompanied by an increase in the activity of sucrose producing enzymes. Similarly, tomato plants genetically modified to produce cytokinin in the roots and sucrose building enzymes in the leaves produce more and heavier fruit when they are grown under salt stress as compared to unmodified tomato. This information will be used by scientists to develop improved crops capable of mitigating the effects of environmental stresses such as high soil and water salt concentrations.

Technical Abstract: Salinization of water and soil has a negative impact on tomato (Solanum lycopersicum L.) crop productivity by reducing growth of sink organs and by inducing senescence in source leaves. It has been hypothesized that yield stability implies the maintenance or increase of sink activity in the reproductive structures, thus contributing to the transport of assimilates from the source leaves, through changes in sucrolytic enzymes and their regulation by phytohormones. Classical and functional physiological approaches have been integrated to study the influence of metabolic and hormonal factors on tomato fruit sink activity, growth and yield: (i) exogenous hormonal applications and (ii) transgenic plants overexpressing the cell wall invertase (cwInv) gene CIN1 in the fruits and de novo cytokinin (CK) biosynthesis gene IPT in the roots. While salinity reduces fruit growth, sink activity and t-zeatin (tZ) concentrations, it increases the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC) during the actively growing period (25 days after anthesis). Indeed, exogenous application of the CK analogue kinetin to salinized actively growing fruits recovered sucrolytic activities (mainly cwInv and sucrose synthase, SUS), sink strength and fruit weight, while the ethylene-releasing compound ethephon had a negative effect in equivalent non-stressed fruits. Both constitutive expression of CIN1 in the fruits or IPT in the root increased fruit number (lower flower abortion) and fruit weight, which was explained by a recovery of sink activity in reproductive tissues due to both (i) increase in sucrolytic activities (cwInv, SUS and vacuolar -vacInv- and cytoplasmic – cytInv- invertases) and t-Z concentration, and (ii) a decrease in the ACC levels and the activity of the invertase inhibitor. This study provides new functional evidences about the role of metabolic and hormonal inter-regulation of local sink processes in controlling tomato fruit sink activity, growth and yield under salinity.