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President's Report

On Monday, June 17, SIVB's Plant Biotechnology Section held a Student Oral Presentation Competition. The top six contestants were chosen to deliver talks based on the quality of their abstracts and five of them were able to present their abstracts at the meeting. All the presentations were good, and the contestants each fielded questions from the audience and our judges. The judges, Dr. Sylvia A. Mitchell, Dr. Mariya Nikolova Somleva, and Dr. Ron Qu’ rendered their final decision and named both Preeti Singh and Deepak Kumar from Jawaharlal Nehru University as tied for first place and Sergio Florez from Penn State University as the winner of 3rd place. Certificates and cash awards were presented at our Plant Section Business Meeting. We encourage all qualified students to enroll in 2014’s competition.

Tied for First Place

Insights into the Role of α-Tocopherol in Plants: Multiple Abiotic Stress Tolerance via ROS Scavenging

Deepak Kumar

Alpha (α)-tocopherol, the biologically most active form of vitamin E, is a major antioxidant that bulwarks the cells against oxidative damage. It constitutes a small fraction of the total tocopherol pool in most oilseed crops. We generated transgenic (TR) Brassica juncea plants with ~6 fold higher α-tocopherol levels compared to the wild type (WT) plants by overexpressing γ-tocopherol methyl transferase. This enzyme catalyzes a rate limiting step in the α-tocopherol biosynthetic pathway. To better understand the roles of different tocopherol forms in plants we compared the performance of TR plants under conditions of abiotic stresses induced by NaCl (salinity), CdCl2 (heavy metal) and mannitol (drought). This resulted in an increase in total tocopherol levels in both the WT and TR plants. Seed germination, shoot growth, and leaf disc senescence showed that TR B. juncea had enhanced tolerance to these stress and that induced by high temperature and methyl viologen. Damage caused by the induced stress was lower in TR plants compared to WT plants as assessed by their higher relative water content, lower MDA and H2O2 accumulation and lower electrolyte leakage. Lesser superoxide and H2O2 accumulation was observed in TR seedlings exposed to these stress. Enhanced levels of different antioxidant enzymes and molecules were present in TR plants when compared to WT plants under similar stress. Analysis of chlorophyll a fluorescence rise kinetics showed that there were differential effects of the applied stress on different sites of the photosynthetic machinery. These effects were found to be alleviated in TR plants. Thus, biofortification by metabolic engineering not only offers sustainable alternative to vitamin E supplementation for improvement of human health but also plays an important role in the alleviation of various environmental stress conditions in plants.

Deepak Kumar. School of Life Sciences, Jawaharlal Nehru University, New Delhi, INDIA. In Vitro Cellular and Developmental Biology, 49:S34, 2013

Tied for First Place

Introgression of a Novel Aldose Reductase from Xerophyta viscose (ALDRXV4) Confers Multiple Stress Tolerance to Evolutionary Diverse Organisms

Preeti Singh

The enzyme aldose reductase plays an important role in the osmo-protection mechanism and detoxification of reactive aldehyde compounds. The aim of this study was to monitor whether over-expression of the aldose reductase homologue ALDRXV4 from the resurrection plant Xerophyta viscosa could provide protection to prokaryotic (E.coli) and eukaryotic (tobacco and blackgram) cells from methylglyoxal (MG) toxicity during abiotic stressess. When over expressed in bacteria, recombinant ALDRXV4 conferred multiple stress tolerance. Furthermore, ALDRXV4 was cloned in a plant expressing vector under constitutive promoter and transformed into model plant tobacco and subsequently used for the transformation of a highly recalcitrant pulse crop, Vigna mungo (blackgram). Compared with wild type plants, transgenics showed improved photosynthetic efficiency, less electrolyte leakage and higher relative water content under drought and salinity stress. The increased synthesis of aldose reductase in the transgenic plants correlated with an elevated level of sorbitol and reduced methylglyoxal (MG) accumulation under stress conditions, consistent with its suggested role in osmoprotection and detoxification. They also showed less membrane damage, favorable ionic balance, and higher chlorophyll content under stress. The transgenic lines showed normal growth, morphology and seed production as compared to the WT plants without any yield penalty under stress conditions. The overall results demonstrate the profound effect of ALDRXV4 in bestowing multiple abiotic stress tolerance at cellular and whole plant level via ROS detoxification. To the best of our knowledge this is the only report of engineering multiple abiotic stress tolerance in blackgram.

Preeti Singh. Jawaharlal Nehru University, New Delhi, India. In Vitro Cellular and Developmental Biology, 49:S35, 2013.

Third Place

Improving the Process of Somatic Embryogenesis Using Transient Expression of Transcription Factors and the implementation of a Novel Bioreactor Design

Sergio Florez

The process of somatic embryogenesis (SE) allows for the propagation of superior plants from non-embryonic tissue. Traits such as disease resistance can be maintained in all the plants generated through SE resulting in a greater economic value. While the process of SE has been commercialized for many economical important crops, the mechanism behind this process is not completely understood. Using cacao (chocolate tree) as a model, we are implementing whole genome transcriptomics to identify the key genes responsible for the reprograming of a somatic cell into an embryo. Further understanding of this regulation will be used to control SE with the goal of making it a more efficient, economical feasible process. Potential transcription factors responsible for this regulation have been isolated and characterized. Preliminary results testing the function of these genes in cacao have led to improvements in embryo production. Overexpression of the transcription factor BABY BOOM resulted in twice as many embryos produced per explant after one hundred days post culture initiation when compared to the control. To fully develop this “enhanced” SE process and show the feasibility of implementing at a commercial scale, we are developing a novel low cost temporary immersion bioreactor. This system will allow genes to be transiently expressed via Agrobacterium-mediated transformation. We are also trying to improve the process by exploring novel Agrobacterium techniques including the use of auxotrophic strains and suicide genes to control overgrowth to increase transformation efficiency. The employment of a bioreactor system to complement a transient gene expression strategy to improve SE can be a very useful platform for the propagation of many commercial crops.

Sergio Florez, Department of Chemical Engineering, Pennsylvania State University, PA. In Vitro Cellular and Developmental Biology, 49:S34, 2013.