부산대학교 도서관

Water availability is one of the major constraints on plant productivity (Boyer, 1982) as well as one of the main factors for the distribution of plant species. The tolerance of a crop to drought stress is essentially related to its ability to access to soil water and its efficiency use. In Spain, tomato is an important and high water consuming crop. Any improvement in water use efficiency (WUE) would imply a significant socioeconomic and environmental impact (e.g. an improvement of 10% in WUE of the greenhouse tomato crop in the Region of Murcia would save is equivalent to the water consumption of a population of 20.000 inhabitants). The experimental section of this thesis has been divided into two parts. Firstly, with the aim of studying the role of invertase in response to drought stress in tomato (Solanum lycopersicon L.), we generated transgenic plants overexpressing the cell wall invertase (cwInv) gene CIN1 from Chenopodium rubrum under the control of a promoter of vacuolar invertase from Solanum pimpinellifolium (InvLp6g). Secondly, we applied a genetic approach to identify and exploit water and/or hormonal-related traits associated with WUE through the use of a population of recombinant inbred lines (RIL) derived from a cross between Solanum lycopersicum and Solanum pimpinellifolium. CIN1 overexpression resulted in a decrease in accumulated transpiration and higher carbon assimilation, thereby increasing WUE compared to wild-type (WT) plants at the end of the drought period (9 days). This seems to be related to a better regulation of source-sink relations by maintaining metabolic fluxes. In addition, anti-oxidative mechanisms were improved in the CIN1 plants. Changes observed in primary metabolism were associated with changes in the hormonal balance. The concentration of the most active cytokinin (CK) in tomato trans-zeatin (t-Z) increased while the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC) decreased in the CIN1 plants respect to WT. Thus, cwInv critically functions at the integration point of metabolic, hormonal and stress signals, providing a novel strategy to overcome drought -induced limitations to crop yield, without negatively affecting plant fitness under optimal growth conditions. Moreover, by using a genetic approach we could identify water- and hormonal-related traits directly involved in WUE regulation. These physiological traits can be directly transferred from the root to the scion through the use of selected RILs as rootstocks, improving crop productivity through root-to-shoot communication. Both the ethylene precursor ACC and ABA concentrations seem to be hormonal signals involved in leaf growth at the end of the experiment with higher transpiration rate. ACC was positively associated with WUEaY (base on fruit yield) and negatively with WUEav (based on vegetative biomass) through down-regulation of leaf area. Additionally, CKs, salicylic acid, ACC and jasmonic acid seem to be positive hormonal parameters regulating leaf growth and WUEa. Therefore, by using a functional approach it has been demonstrated that invertases play an important role in abiotic stress adaptation through a regulation in the hormonal balance. On the other hand, by using a genetic approach employing RIL lines we identified hormonal characters (mostly ACC and CKs), involved in the regulation of WUE in tomato and, thereafter, we exploited those characters to improve productivity crop thought the use of grafting.