On Monday, June 4, SIVB held an oral presentation competition for post-doctoral scientists. The top five contestants had been chosen to deliver talks based on the quality of their abstracts. There was a large turnout for the event. All the presentations were good, and the contestants each fielded questions from the audience and our judges. Since the scientific topics were diverse it was difficult to compare the topics and choose a winner; however, our judges Dr. Nancy Reichert, Dr. C. S. Prakash Kumar, and Dr. John Finer were able to render a final decision. They selected M. Aydin Akbudak for 3rd prize, Meredith Cook for 2nd prize, and Sherif Sherif for 1st prize. The next day at our Plant Section Business Meeting, plaques and cash awards were made. We encourage all qualified scientists to enroll in 2013’s competition.
Submitted by Hong Luo
First Place
Sherif Sheriif
A Novel JAZ1 Protein from Peach Negatively Regulates Flower Opening and Is Not Degraded by the Ubiquitin/26S Proteasome Pathway
Flower opening is indispensable for fruit set in stone fruits where most plum, cherry and some apricot varieties are self-incompatible and require cross-pollination for fruit set. In contrast, the vast majority of peach varieties are self-fruitful and they can carry either showy chasmogamous (CH) or preanthesis cleistogamous (CL) flowers. The application of methyl jasmonate (MeJA) could fasten petal elongation and flower opening of CL varieties. Two peach accessions, namely V85331and VABM29, were used as representatives for CL and CH flowers, respectively, in order to investigate the role of JA pathway components on regulating flower opening. JA-biosynthesis genes; e.g. Pp-LOX3, Pp-OPR3 and Pp-AOC showed slight changes in transcripts level before and after anthesis in both types of flowers. Nevertheless, the genes encode for JAZs, the key repressors of JA signaling, showed significant differences in gene expression between VABM29 and V85331. Transcripts of Pp-JAZ1, in particular, were more abundant in CL flowers after anthesis indicating a potential role of this gene in flower closure. To test this hypothesis, we cloned this Pp-JAZ1 gene and overexpressed it in tobacco. Transgenic tobacco expressing Pp-JAZ1 exhibited CL flowers. The exogenous application of MeJA could partially restore the anthesis of CL flowers, suggesting a suppressive role of Pp-JAZ1 into JA-mediated flower opening. JA-insensitivity in transgenic plants is attributed to enhanced stability of Pp-JAZ1. This became evident after Pp-JAZ1-GFP chimeric protein expressed in peach leaves remained intact after 60 min of MeJA application, while its Arabidopsis orthologue (At-JAZ1) was degraded completely within 30 min. Further analysis using yeast two-hybrid assay indicated that Pp-JAZ1 is not interacting with Pp-COI1, the JA receptor and the part of SCFCOI1 ubiquitin ligase. The comparison between Pp-JAZ1 and At-JAZ1 identified amino acid substitution in Jas domain that might be essential for Pp-JAZ1 interaction with Pp-COI1 and subsequently its degradation by the ubiquitin/26S proteasome pathway.
Sherif Sheriif, Department of Plant Agriculture, University of Guelph, Guelph ON and Vineland Research Station, Department of Plant Agriculture, University of Guelph, Guelph ON, CANADA.In Vitro Cellular and Developmental Biology, 48:S42, 2012
Second place
Meridith Cook
Recombinase-mediated Technologies for Production of Plants and Microbes with Enhanced Traits
Biotechnology offers many opportunities for crop improvement. Recombinase-mediated cassette exchange (RMCE) is a strategy that can be used to genetically modify plants in a precise manner, and allows production of selectable marker-free plants. RMCE involves the use of site-specific recombinases to both integrate and excise sequences of interest. The initial step in RMCE is production of “founder” lines, which contain the recombinase recognition sites flanking a selectable marker, referred to as the “TAG” region. Transformation of the founder lines with an incoming “exchange” vector results in two recombination reactions: first, integration of the entire exchange vector occurs, and then excision of the region between the excision-specific recognition sites takes place. The RMCE strategy used in this study was first tested in the eukaryotic model system Saccharomyces cerevisiae (brewers’ yeast). Yeast founder lines were produced and subsequently transformed with an exchange vector. Integration of the exchange vector was followed by the predicted excision event, resulting in the “swapping” of the selectable marker for the gene of interest. Both events were verified using PCR and phenotypic assays. This technology is currently being utilized to engineer yeast for improved biofuel production. Furthermore, these yeast experiments demonstrate that the RMCE strategy is functional and give support for further testing in plants. The plant system used to test RMCE was the oilseed crop Camelina sativa. Founder C. sativa lines containing recombinase recognition sites were produced using the herbicide resistance gene bar or the antibiotic resistance gene hptII and were confirmed using PCR and Southern blot analyses. An exchange vector is currently being investigated that will allow site-specific integration of a gene(s) of interest followed by excision of the unneeded markers. The RMCE strategy presented here has widespread applications in both plant and microbial systems for precise engineering of enhanced traits of interest.
Meridith Cook, USDA-ARS-WRRC, Crop Improvement and Utilization Research Unit, Albany, CA 94710. In Vitro Cellular and Developmental Biology, 48:S36-37, 2012
Third Place
M. Aydin Akbudak
Gene Silencing in Multiple Arabidopsis Genes by Terminator-less Transgene Constructs
Transgene-mediated gene silencing is a prominent biotechnology and research tool. There are several RNAi-mediated techniques available for silencing genes in plants. The basis of all these techniques is to stimulate the generation of double stranded RNA precursors in the cell, which are recognized by the surveillance system in the cell and marked for degradation by the dicer family RNases into siRNAs. Improperly terminated, unpolyadenylated RNA are potent precursors of double stranded RNA and therefore considered as silencing triggers in plants. Such transcripts can easily be synthesized from transgene constructs lacking transcription-terminator signals (terminator-less constructs). The present study determined the efficiency of terminator-less constructs on 4 different genes in Arabidopsis, VAR2, AP1, BRI1 and CO. Expression of terminator-less VAR2, AP1, BRI1 and CO constructs resulted in dramatic decline in transcript level up to 90% compared to wild type. This suppression was accompanied with mutant phenotype in selected transgenic lines. Thus, terminator-less constructs are efficient tools for inducing silencing of genes in plants.
M. Aydin Akbudak, Department of Crop, Soil & Environmental Sciences, University of Arkansas, Fayetteville, AR 72701. In Vitro Cellular and Developmental Biology, 48:S37-38, 2012
