Genetic manipulation of protein phosphatase 2A affects multiple agronomic traits and physiological parameters in potato ().

In this study, agronomic and functional characteristics of potato (Solanum tuberosum ) plants constitutively overexpressing the protein phosphatase 2A (PP2A) catalytic subunit StPP2Ac2b (StPP2Ac2b-OE) were evaluated. StPP2Ac2b-OE plants display reduced vegetative growth, tuber yield and tuber weight under well-watered and drought conditions. Leaves of StPP2Ac2b-OE plants show an increased rate of water loss, associated with an impaired ability to close stomata in response to abscisic acid.

Impact of polyploidy on plant tolerance to abiotic and biotic stresses.

Polyploidy, defined as the coexistence of three or more complete sets of chromosomes in an organism's cells, is considered as a pivotal moving force in the evolutionary history of vascular plants and has played a major role in the domestication of several crops. In the last decades, improved cultivars of economically important species have been developed artificially by inducing autopolyploidy with chemical agents. Studies on diverse species have shown that the anatomical and physiological changes generated by either natural or artificial polyploidization can increase tolerance to abiotic and biotic stresses as well as disease resistance, which may positively impact on plant growth and net production.

TuMV triggers stomatal closure but reduces drought tolerance in Arabidopsis.

Compatible plant viral infections are a common cause of agricultural losses worldwide. Characterization of the physiological responses controlling plant water management under combined stresses is of great interest in the current climate change scenario. We studied the outcome of TuMV infection on stomatal closure and water balance, hormonal balance and drought tolerance in Arabidopsis.

The cytosolic invertase NI6 affects vegetative growth, flowering, fruit set, and yield in tomato.

Sucrose metabolism is important for most plants, both as the main source of carbon and via signaling mechanisms that have been proposed for this molecule. A cleaving enzyme, invertase (INV) channels sucrose into sink metabolism. Although acid soluble and insoluble invertases have been largely investigated, studies on the role of neutral invertases (A/N-INV) have lagged behind.

Growth promotion and protection from drought in Eucalyptus grandis seedlings inoculated with beneficial bacteria embedded in a superabsorbent polymer.

Eucalyptus grandis is a globally important tree crop. Greenhouse-grown tree seedlings often face water deficit after outplanting to the field, which can affect their survival and establishment severely. This can be alleviated by the application of superabsorbent hydrophilic polymers (SAPs).

Water deficit stress tolerance in maize conferred by expression of an isopentenyltransferase (IPT) gene driven by a stress- and maturation-induced promoter.

Senescence can be delayed in transgenic plants overexpressing the enzyme isopentenyltransferase (IPT) due to stress-induced increased levels of endogenous cytokinins. This trait leads to sustained photosynthetic activity and improved tolerance to abiotic stress. The aim of this study was to generate and characterize transgenic plants of maize (Zea mays L.

Replacement of alpha-tocopherol by beta-tocopherol enhances resistance to photooxidative stress in a xanthophyll-deficient strain of Chlamydomonas reinhardtii.

Tocopherols (vitamin E) comprise a class of lipid-soluble antioxidants synthesized only in plants, algae, and some cyanobacteria. The majority of tocopherols in photosynthetic cells is in the alpha form, which has the highest vitamin E activity in humans, whereas the beta, gamma, and delta forms normally account for a small percentage of total tocopherols. The antioxidant activities of these forms of tocopherol differ depending on the experimental system, and their relative activities in vivo are unclear.

The contribution of photosynthesis to the red light response of stomatal conductance.

To determine the contribution of photosynthesis on stomatal conductance, we contrasted the stomatal red light response of wild-type tobacco (Nicotiana tabacum 'W38') with that of plants impaired in photosynthesis by antisense reductions in the content of either cytochrome b(6)f complex (anti-b/f plants) or Rubisco (anti-SSU plants). Both transgenic genotypes showed a lowered content of the antisense target proteins in guard cells as well as in the mesophyll. In the anti-b/f plants, CO(2) assimilation rates were proportional to leaf cytochrome b(6)f content, but there was little effect on stomatal conductance and the rate of stomatal opening.

Photo-oxidative stress in a xanthophyll-deficient mutant of Chlamydomonas.

When there is an imbalance between the light energy absorbed by a photosynthetic organism and that which can be utilized in photosynthesis, photo-oxidative stress can damage pigments, proteins, lipids, and nucleic acids. In this work we compared the wild type and a xanthophyll-deficient mutant of Chlamydomonas reinhardtii in their response to high amounts of light. Wild-type Chlamydomonas cells were able to acclimate to high amounts of light following transfer from low light conditions.

Zeaxanthin accumulation in the absence of a functional xanthophyll cycle protects Chlamydomonas reinhardtii from photooxidative stress.

Xanthophylls participate in light harvesting and are essential in protecting the chloroplast from photooxidative damage. To investigate the roles of xanthophylls in photoprotection, we isolated and characterized extragenic suppressors of the npq1 lor1 double mutant of Chlamydomonas reinhardtii, which lacks zeaxanthin and lutein and undergoes irreversible photooxidative bleaching and cell death at moderate to high light intensities. Here, we describe three suppressor strains that carry point mutations in the coding sequence of the zeaxanthin epoxidase gene, resulting in the constitutive accumulation of zeaxanthin in a range of concentrations.

Photoinhibition and repair in Dunaliella salina acclimated to different growth irradiances.

The light-dependent rate of photosystem-II (PSII) damage and repair was measured in photoautotrophic cultures of Dunaliella salina Teod. grown at different irradiances in the range 50-3000 μmol photons · m· s. Rates of cell growth increased in the range of 50-800 μmol photons·m·s, remained constant at a maximum in the range of 800-1,500 μmol photons·m ·s, and declined due to photoinhibition in the range of 1500-3000 μmol photons·m·s.