The phenotype alterations showed by the res tomato mutant disappear when the plants are grown under semi-arid conditions: Is the res mutant tolerant to multiple stresses?

The res (restored cell structure by salinity) mutant, recently identified as the first tomato mutant accumulating jasmonate (JA) without stress, exhibited important morphological alterations when plants were grown under control conditions but these disappeared under salt stress. Since the defense responses against stresses are activated in the res mutant as a consequence of the increased expression of genes from the JA biosynthetic and signaling pathways, the mutant may display a tolerance response not only to salt stress but also to multiple stresses. Here, we show that when res mutant plants are grown under the summer natural conditions of the Mediterranean area, with high temperatures and low relative humidity, the characteristic leaf chlorosis exhibited by the mutant disappears and leaves become dark green over time, with a similar aspect to WT leaves.

The tomato res mutant which accumulates JA in roots in non-stressed conditions restores cell structure alterations under salinity.

Jasmonic acid (JA) regulates a wide spectrum of plant biological processes, from plant development to stress defense responses. The role of JA in plant response to salt stress is scarcely known, and even less known is the specific response in root, the main plant organ responsible for ionic uptake and transport to the shoot. Here we report the characterization of the first tomato (Solanum lycopersicum) mutant, named res (restored cell structure by salinity), that accumulates JA in roots prior to exposure to stress.

Heterologous expression of the yeast HAL5 gene in tomato enhances salt tolerance by reducing shoot Na+ accumulation in the long term.

For salt tolerance to be achieved in the long-term plants must regulate Na(+)/K(+) homeostasis over time. In this study, we show that the salt tolerance induced by overexpression of the yeast HAL5 gene in tomato (Solanum lycopersicum) was related to a lower leaf Na(+) accumulation in the long term, by reducing Na(+) transport from root to shoot over time regardless of the severity of salt stress. Furthermore, maintaining Na(+)/K(+) homeostasis over time was associated with changes in the transcript levels of the Na(+) and K(+) transporters such as SlHKT1;2 and SlHAK5.

Overexpression of dehydrin tas14 gene improves the osmotic stress imposed by drought and salinity in tomato.

One strategy to increase the level of drought and salinity tolerance is the transfer of genes codifying different types of proteins functionally related to macromolecules protection, such as group 2 of late embryogenesis abundant (LEA) proteins or dehydrins. The TAS14 dehydrin was isolated and characterized in tomato and its expression was induced by osmotic stress (NaCl and mannitol) and abscisic acid (ABA) [Godoy et al., Plant Mol Biol 1994;26:1921-1934], yet its function in drought and salinity tolerance of tomato remains elusive.

An insertional mutagenesis programme with an enhancer trap for the identification and tagging of genes involved in abiotic stress tolerance in the tomato wild-related species Solanum pennellii.

Salinity and drought have a huge impact on agriculture since there are few areas free of these abiotic stresses and the problem continues to increase. In tomato, the most important horticultural crop worldwide, there are accessions of wild-related species with a high degree of tolerance to salinity and drought. Thus, the finding of insertional mutants with other tolerance levels could lead to the identification and tagging of key genes responsible for abiotic stress tolerance.

The HAL1 function on Na+ homeostasis is maintained over time in salt-treated transgenic tomato plants, but the high reduction of Na+ in leaf is not associated with salt tolerance.

To achieve a deeper knowledge on the function of HAL1 gene in tomato (Solanum lycopersicum) plants submitted to salt stress, in this study, we studied the growth and physiological responses to high salt stress of T3 transgenic plants (an azygous line without transgene and both homozygous and hemizygous lines for HAL1) proceeding from a primary transformant with a very high expression level of HAL1 gene. The homozygous plants for HAL1 gene did not increase their salt tolerance in spite of an earlier and higher reduction of the Na(+) accumulation in leaves, being moreover the Na(+) homeostasis maintained throughout the growth cycle. The greater ability of the homozygous line to regulate the Na(+) transport to the shoot to long term was even shown in low accumulation of Na(+) in fruits.