The following student awards were presented at the 2011 In Vitro Biology Meeting, Raleigh, North Carolina. Information related to the available specific student awards can be found on the SIVB website (www.sivb.org) or by contacting the SIVB Business Office at (919) 562-0600, email@example.com, or Dr. Pamela Weathers, Chair, Student Affairs and Awards Committee, at firstname.lastname@example.org.
2011 WILTON R. EARLE AWARD AND
2011 SIVB STUDENT TRAVEL AWARD
Rooting for Artemisinin in Artemisia annua Shoots
Artemisinin, synthesized in glandular trichomes of Artemisia annua, is the most effective treatment for malaria, but since the plantproduces so little of the drug, supply is inadequate to cost effectively treat all infected patients. Although the biosynthetic pathway is reasonably elucidated, little is known on how the pathway is regulated. A. annua shoots produce less artemisinin than rooted shoots. No artemisinin or its pathways metabolites are produced in the plant’s roots. Furthermore, rooted shoots respond to some signals, e.g. DMSO, but shoots do not, suggesting the roots are altering some aspect of the pathway. We measured trichome populations, and gene transcripts and metabolites in the artemisinin pathway in shoots as they form roots. Shoots were inoculated into either shooting or rooting medium for 16 days and plants were harvested periodically for analysis. Metabolites were analyzed via GC-MS and the first 3 genes in the pathway (ADS, CYP, DBR2) were measured using qPCR. As roots began to form, the end products of several branches of the pathway increased, but two of their immediate precursors remained high in the shoots. Consistent with these results, there was no difference in the mRNA transcript levels of the 3 genes. Although trichome number did not change, they were larger after roots formed. It is possible that roots do not regulate the transcription of the genes in the pathway, but instead, regulate the last non-enzymatic and photo-oxidative step in the pathway. Roots also seem to affect trichome size. When rooted shoots were transferred to either shooting or rooting medium, there was no significant difference in artemisinic metabolites in the shoots from either medium even after 20 days. This suggested that once roots develop, the artemisinin pathway is committed and the two phytohormones present within shooting medium (NAA and BAP) are unable to inhibit the pathway. Future work will explore how NAA and BAP impact trichomes and the artemisinin biosynthetic pathway.
Khanhvan T. Nguyen,Worcester Polytechnic Institute, 100 Institute Road, Gateway Park – BB Dept. Worcester, MA 01609. In Vitro Cellular and Developmental Biology, 47:S36, 2011
2011 JOHN S. SONG AWARD AND
2011 SIVB STUDENT TRAVEL AWARD
The Role of Antioxidant Vitamin E Supplementation In Brassica juncea Plants: Regulation and Function Under Abiotic Stress
Tocopherols (Vitamin E) are essential nutrients in mammalian diets and are exclusively synthesized by oxygen evolving phototrophs, including some cyanobacteria and all green algae and plants. They are very potent antioxidants protecting polyunsaturated fatty acids in the membranes from peroxidation and their higher dietary intakes are, thus, implicated in protection against various diseases including cancer. Out of the four types of tocopherols (α, β, γ, and δ), which differ only in the number and position of methyl substituents on the chromanol ring, α-Tocopherol has the highest biological activity, but constitutes only a small fraction of the total tocopherol pool in most of the oil seed crops, the major sources of vitamin E. To increase the human intake of this vitamin we successfully fortified transgenic Brassica juncea plants with α-tocopherol (~6 fold increase as compared to the control plants) by overexpression of γ-tocopherol methyl transferase which catalyzes a rate limiting step in the α-tocopherol biosynthetic pathway. . Further, to better understand the roles of different tocopherol forms in plants, which have not been studied exhaustively, we compared the physiological and photosynthetic performance of α-tocopherol enriched transgenic and untransformed control B. juncea plants under conditions of induced abiotic stresses. We found that abiotic stress induced by NaCl (salinity), CdCl2 (heavy metal), and mannitol (drought) resulted in an increase in the total tocopherol levels in both the control and transgenic plants. Comparisons of seed germination, shoot growth, leaf disc senescence and measurement of antioxidant enzymes showed that transgenic B. juncea plants had enhanced tolerance to the induced stress. Analysis of the chlorophyll a fluorescence rise kinetics, from the initial “O” level to the “P” (peak) level, 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 the transgenic plants. These results provide newer insights into the protective role of α-tocopherol in plants exposed to abiotic stress. The α-tocopherol enriched oilseed crops could, therefore, serve a dual purpose, that of increasing the natural α-tocopherol content in human diets and helping the plants to better cope with the abiotic stress conditions.
Deepak Kumar, Jawaharlal Nehru University, c/o, Prof. Neera Bhalla Sarin, Lab No# 308, School of Life Sciences, New Delhi, Delhi 110067, India. In Vitro Cellular and Developmental Biology, 47:S76-77, 2011
2011 PHILIP R. WHITE AWARD AND
2011 SIVB STUDENT TRAVEL AWARD
RNA Interference Suppresses Lignin Biosynthetic Genes Caffeic Acid 3-O-methyltransferase (COMT) and/or 4-coumarate-CoA Ligase (4CL) in Sugarcane
A large amount of lignocellulosic biomass such as leaf litter residues and bagasse are generated during the sugarcane harvest or after the sugar refining process, respectively. Therefore, lignocellulosic biomass from leaf and processing residues will likely become a valuable feedstock for future biofuel production. However, lignin is recognized as the major limitation to efficient conversion of lignocellulosic biomass to biofuel. Therefore, altering lignin composition or reducing lignin content via RNAi suppression of lignin biosynthetic genes is a promising strategy to increase the efficiency of biofuel production from lignocellulosic sugarcane residues. In the lignin pathway, 4-coumarate-CoA ligase (4CL) and caffeic acid 3-O-methyltransferase (COMT) are key enzymes that catalyze the formation of CoA thiol esters of 4-coumarate and other hydroxycinnamates or the methylation of 5-hydroxyconiferaldehyde to sinapaldehyde, respectively. In this study, COMT and 4CL genes were isolated from the commercially important sugarcane cultivar CP 88-1762 by a combination of cDNA library screening and PCR based approaches. More than 100 transgenic lines harboring COMTi or 4CLi or both COMTi and 4CLi constructs were generated via biolistic gene transfer. Quantitative real-time PCR identified transgenic lines ranging from no suppression to almost complete suppression of the target genes. Accumulation of siRNAs was confirmed in 23 transgenic lines by Northern blot analysis of low molecular weight RNA. These transgenic lines were vegetatively propagated and are currently grown to maturity in a replicated and randomized design. The analysis of the Klason lignin content will be carried out in the Spring of 2011 and presented at the conference. These results demonstrate that RNAi is effective in suppression of individual or co-suppression of multiple endogenous genes of the complex sugarcane genome. Further these results allow a determination of the relative importance of the targeted alleles or gene families for lignin biosynthesis and biofuel applications in sugarcane.
Je Hyeong Jung, University of Florida-IFAS, Agronomy Dept., Plant Molecular and Cellular Biology Program, Genetics Institute, Gainesville, FL 32611. In Vitro Cellular and Developmental Biology, 47:S31, 2011.