Jawaharlal Nehru University

About: Jawaharlal Nehru University is a education organization based out in New Delhi, India. It is known for research contribution in the topics: Population & Politics. The organization has 6082 authors who have published 13455 publications receiving 245407 citations. The organization is also known as: JNU.

Drug resistance in Plasmodium

Abstract: Haldar and colleagues discuss markers and mechanisms of resistance to artemisinins and artemisinin-based combination therapies. They describe the identification of Plasmodium falciparum Kelch 13 as the primary and, to date, sole causative maker of artemisinin resistance in P. falciparum and explore two proposed resistance mechanisms. They emphasize continuing challenges to improve detection strategies and new drug development strategies.

Chlorophyll a fluorescence induction: a personal perspective of the thermal phase, the J–I–P rise

Abstract: The fast (up to 1 s) chlorophyll (Chl) a fluorescence induction (FI) curve, measured under saturating continuous light, has a photochemical phase, the O–J rise, related mainly to the reduction of QA, the primary electron acceptor plastoquinone of Photosystem II (PSII); here, the fluorescence rise depends strongly on the number of photons absorbed. This is followed by a thermal phase, the J–I–P rise, which disappears at subfreezing temperatures. According to the mainstream interpretation of the fast FI, the variable fluorescence originates from PSII antenna, and the oxidized QA is the most important quencher influencing the O–J–I–P curve. As the reaction centers of PSII are gradually closed by the photochemical reduction of QA, Chl fluorescence, F, rises from the O level (the minimal level) to the P level (the peak); yet, the relationship between F and [QA −] is not linear, due to the presence of other quenchers and modifiers. Several alternative theories have been proposed, which give different interpretations of the O–J–I–P transient. The main idea in these alternative theories is that in saturating light, QA is almost completely reduced already at the end of the photochemical phase O–J, but the fluorescence yield is lower than its maximum value due to the presence of either a second quencher besides QA, or there is an another process quenching the fluorescence; in the second quencher hypothesis, this quencher is consumed (or the process of quenching the fluorescence is reversed) during the thermal phase J–I–P. In this review, we discuss these theories. Based on our critical examination, that includes pros and cons of each theory, as well mathematical modeling, we conclude that the mainstream interpretation of the O–J–I–P transient is the most credible one, as none of the alternative ideas provide adequate explanation or experimental proof for the almost complete reduction of QA at the end of the O–J phase, and for the origin of the fluorescence rise during the thermal phase. However, we suggest that some of the factors influencing the fluorescence yield that have been proposed in these newer theories, as e.g., the membrane potential ΔΨ, as suggested by Vredenberg and his associates, can potentially contribute to modulate the O–J–I–P transient in parallel with the reduction of QA, through changes at the PSII antenna and/or at the reaction center, or, possibly, through the control of the oxidation–reduction of the PQ-pool, including proton transfer into the lumen, as suggested by Rubin and his associates. We present in this review our personal perspective mainly on our understanding of the thermal phase, the J–I–P rise during Chl a FI in plants and algae.

Glyoxalase I from Brassica juncea: molecular cloning, regulation and its over-expression confer tolerance in transgenic tobacco under stress.

Abstract: Despite its ubiquitous presence, the role of glyoxalase I has not been well investigated in plants. In order to find out its physiological functions, we have cloned and characterized a cDNA from Brassica juncea encoding glyoxalase I (Gly I) and made transgenic tobacco plants harbouring Gly I in both sense and antisense orientation. The transgenic nature of the plants was confirmed by Southern blotting, and the estimated number of genes inserted ranged from one to six. The transcript and protein levels of glyoxalase I were also monitored in transgenic plants. The expression of glyoxalase I in B. juncea was upregulated in response to salt, water and heavy metal stresses. In response to a high concentration of salt, the transcript level averaged threefold higher in 72 h, and an increase in the protein was also seen by immunoblotting. The transgenic plants over-expressing glyoxalase I showed significant tolerance to methylglyoxal and high salt, as tested in detached leaf disc senescence assay. A comparison of plants expressing high and low levels of glyoxalase I showed that the tolerance to different salt concentrations was correlated with the degree of glyoxalase I expression. Our results suggest an important role of glyoxalase I in conferring tolerance to plants under stress conditions.