Biomedical subjects

Baldeep Kular

Publications and source records attributed to Baldeep Kular.

4 recordsLinked to original sources

PubMed2006

Controlled levels of salicylic acid are required for optimal photosynthesis and redox homeostasis.

Sudden exposure of plants to high light (HL) leads to metabolic and physiological disruption of the photosynthetic cells. Changes in ROS content, adjustment of photosynthetic processes and the antioxidant pools and, ultimately, gene induction are essential components for a successful acclimation to the new light conditions. The influence of salicylic acid (SA) on plant growth, short-term acclimation to HL, and on the redox homeostasis of Arabidopsis thaliana leaves was assessed here. The dwarf phenotype displayed by mutants with high SA content (cpr1-1, cpr5-1, cpr6-1, and dnd1-1) was less pronounced when these plants were grown in HL, suggesting that the inhibitory effect of SA on growth was partly overcome at higher light intensities. Moreover, higher SA content affected energy conversion processes in low light, but did not impair short-term acclimation to HL. On the other hand, mutants with low foliar SA content (NahG and sid2-2) were impaired in acclimation to transient exposure to HL and thus predisposed to oxidative stress. Low and high SA levels were strictly correlated to a lower and higher foliar H(2)O(2) content, respectively. Furthermore high SA was also associated with higher GSH contents, suggesting a tight correlation between SA, H(2)O(2) and GSH contents in plants. These observations implied an essential role of SA in the acclimation processes and in regulating the redox homeostasis of the cell. Implications for the role of SA in pathogen defence signalling are also discussed.

Acclimatization↗

PubMed2005

Toward supportive data collection tools for plant metabolomics.

Over recent years, a number of initiatives have proposed standard reporting guidelines for functional genomics experiments. Associated with these are data models that may be used as the basis of the design of software tools that store and transmit experiment data in standard formats. Central to the success of such data handling tools is their usability. Successful data handling tools are expected to yield benefits in time saving and in quality assurance. Here, we describe the collection of datasets that conform to the recently proposed data model for plant metabolomics known as ArMet (architecture for metabolomics) and illustrate a number of approaches to robust data collection that have been developed in collaboration between software engineers and biologists. These examples also serve to validate ArMet from the data collection perspective by demonstrating that a range of software tools, supporting data recording and data upload to central databases, can be built using the data model as the basis of their design.

Arabidopsis↗

PubMed2004

Evidence for a direct link between glutathione biosynthesis and stress defense gene expression in Arabidopsis.

The mutant regulator of APX2 1-1 (rax1-1) was identified in Arabidopsis thaliana that constitutively expressed normally photooxidative stress-inducible ASCORBATE PEROXIDASE2 (APX2) and had >/=50% lowered foliar glutathione levels. Mapping revealed that rax1-1 is an allele of gamma-GLUTAMYLCYSTEINE SYNTHETASE 1 (GSH1), which encodes chloroplastic gamma-glutamylcysteine synthetase, the controlling step of glutathione biosynthesis. By comparison of rax1-1 with the GSH1 mutant cadmium hypersensitive 2, the expression of 32 stress-responsive genes was shown to be responsive to changed glutathione metabolism. Under photo-oxidative stress conditions, the expression of a wider set of defense-related genes was altered in the mutants. In wild-type plants, glutathione metabolism may play a key role in determining the degree of expression of defense genes controlled by several signaling pathways both before and during stress. This control may reflect the physiological state of the plant at the time of the onset of an environmental challenge and suggests that changes in glutathione metabolism may be one means of integrating the function of several signaling pathways.

Arabidopsis↗

PubMed2001

Changes in oxidative processes and components of the antioxidant system during tomato fruit ripening.

Analysis of the oxidative processes taking place during fruit ripening in a salad tomato variety (Lycopersicon esculentum Mill. cv. Ailsa Craig) revealed changes in oxidative and antioxidative parameters. Hydrogen peroxide content, lipid peroxidation and protein oxidation were measured as indices of oxidative processes and all were found to increase at the breaker stage. The levels of the aqueous-phase antioxidants, glutathione and ascorbate, increased during the ripening process and these increases were associated with significant changes in their redox status, becoming more reduced as ripening progressed. Changes in the activities of superoxide dismutase, catalase and the enzymes involved in the ascorbate-glutathione cycle during ripening indicated that the antioxidative system plays a fundamental role in the ripening of tomato fruits.

Antioxidants↗