Festuca arundinacea is one of the most drought-tolerant species within the Lolium-Festuca complex and was used as a model for research aimed at identifying the chloroplast components involved in the proteomic response for drought stress in forage grasses. Individual F. arundinacea genotypes with contrasting levels of drought tolerance, the high-drought-tolerant (HDT) and the low-drought-tolerant (LDT) genotypes, were selected for comparative physiological and proteomic work. Measurements of water uptake, chlorophyll fluorescence, relative water content, electrolyte leakage, and gas exchange during drought and rewatering periods were followed by investigations on accumulation levels of chloroplast proteins before drought conditions, on d 3 and 11 of drought treatment, and after 10 d of subsequent watering, using two-dimensional gel electrophoresis. The proteins that were accumulated differentially between the selected plants were then identified by mass spectrometry. The LDT genotype revealed lower levels of water uptake and relative water content as drought progressed, and this was accompanied by lower levels of transpiration and net photosynthesis, and a higher level of electrolyte leakage observed in this genotype. Eighty-two protein accumulation profiles were compared between the HDT and LDT genotypes and ten proteins were shown to be differentially accumulated between them. The functions of the selected proteins in plant cells and their probable influence on the process of recovery after drought treatment in F. arundinacea are discussed.

Festuca arundinacea is a drought tolerant species. Lolium multiflorum has better forage quality but lower tolerance to abiotic stresses. Their hybrids offer an opportunity to perform research on the molecular basis of tolerance to drought. The aim of this work was to recognise the mechanisms of response to short-term drought (11 days) in a glasshouse in two L. multiflorum/F. arundinacea introgression forms with distinct levels of tolerance to long-term drought (14 weeks) in the field. Measurements of physiological parameters, analyses of protein accumulation profiles using two-dimensional gel electrophoresis, and mass spectrometry identification of proteins, which were accumulated differentially between the selected genotypes during short-term drought, were performed. Genotype 7/6, with lower yield potential during 14 weeks of drought, and lower ability to re-grow after watering, had a higher capacity for photosynthesis during 11 days of drought. Genotype 4/10, more tolerant to long-term drought, was able to repair damaged cell membranes after watering and was also characterised by lower transpiration during short-term drought. A total of 455 proteins were analysed, and the 17 that were differentially accumulated between the two genotypes were identified. The results of physiological and proteomic research led to a hypothesis that the higher photosynthetic capacity of genotype 7/6 could be due to a more efficient Calvin cycle, supported by higher accumulation of crucial proteins involving chloroplast aldolase.

Understanding how plants respond to drought at different levels of cell metabolism is an important aspect of research on the mechanisms involved in stress tolerance. Furthermore, a dissection of drought tolerance into its crucial components by the use of plant introgression forms facilitates to analyze this trait more deeply. The important components of plant drought tolerance are the capacity for photosynthesis under drought conditions, and the ability of cellular membrane regeneration after stress cessation. Two closely related introgression forms of Lolium multiflorum/Festuca arundinacea, differing in the level of photosynthetic capacity during stress, and in the ability to regenerate their cellular membranes after stress cessation, were used as forage grass models in a primary metabolome profiling and in an evaluation of chloroplast 1,6-bisphosphate aldolase accumulation level and activity, during 11 days of water deficit, followed by 10 days of rehydration. It was revealed here that the introgression form, characterized by the ability to regenerate membranes after rehydration, contained higher amounts of proline, melibiose, galactaric acid, myoinositol and myo-inositol-1-phosphate involved in osmoprotection and stress signaling under drought. Moreover, during the rehydration period, this form also maintained elevated accumulation levels of most the primary metabolites, analyzed here. The other introgression form, characterized by the higher capacity for photosynthesis, revealed a higher accumulation level and activity of chloroplast aldolase under drought conditions, and higher accumulation levels of most photosynthetic products during control and drought periods. The potential impact of the observed metabolic alterations on cellular membrane recovery after stress cessation, and on a photosynthetic capacity under drought conditions in grasses, are discussed.