To support the Society’s vision to encourage education and scientific informational exchange and recognize outstanding post docs, the Plant Biotechnology Section held a Plant Biotechnology Post-doctoral Oral Presentation Competition on Monday June 4th. A panel of judges evaluated the presentations using the following criteria: experimental design, data analysis, proper interpretation of the results, originality of the study, technical difficulty, appearance and ability of the post-doctoral candidate to present it. The judges were Dr. Prakash Kumar from the National University of Singapore and Dr. Ajith Anand from Corteva Agriscience™, agricultural division of DowDuPont™. Dr. Hoang H Nguyen from University of California Davis received the first prize for his talk “Development of meristem tip culture procedure for eradication of Cherry Virus-A in selected cultivars of Cherry” followed by Dr. Ningning Zhang (second prize) from Donald Danforth Plant Science Center for her talk “Acquired thermotolerance and heat stress memory in Chlamydomonas reinhardtii”.

Submitted by Geny Anthony

First Place

Development of a Meristem-tip Culture Procedure for Eradication of Cherry Virus-A in Selected Cultivars of Cherry

Cherry virus A (CVA), a recently-discovered asymptomptic virus that belongs to the genus Capillovirus, appears to be wide spread in many commercial cherry cultivars. Although the effects of this virus are not yet established, the movement of cherry germplasm, even from elite collections, between States can be restricted if the virus is known to infect the material. Movement of cherry stocks between California, Oregon, and Washington has been impeded due to regulatory exclusion of this wide-spread virus. Work was conducted to optimize a meristem-tip culture procedure for eradication of CVA in selected Prunus cultivars. Infection status of four non-symptomatic cherry cultivars (Prunus spp.) was confirmed by RT-qPCR. CVA was detected in three out of four tested cultivars. Lateral shoots from the CVA-negative cherry trees (P. lannesiana cv. ‘Krymsk ®7, or P2G9) were used as an explant source for media evaluation and meristem culture experiments, while three CVA infected cherry cultivars (P. avium x P. tomentosa cv. Montmorency, P. cerasus cv. English Morello, P. serrulata cv. Pink Cloud) were used as material for CVA eradication. Meristem-tips of P2G9 (0.5-0.7 mm), from in vitro plants and field-grown trees, were established with highest succesful rates on WPM (1981) media supplemented with 0.5mg/L meta-topolin (95% from in vitro plants and 17.5% for field-grown plants). Meristems of CVA-infected cultivars’ survival rates ranged from 45-64%. In vitro shoots of four cultivars were rooted in vitro using IBA-pulse (10 mg/L) in combination with dark treatment. Rooted plant were successfully transferred to soil. Although further testing are required, our preliminary testing, conducted on in vitro plants, showed 91% negative for the virus (all P. cv. Montmorency).

Nguyen H. Hoang, University of California, Davis, Davis, CA. In Vitro Cellular and Developmental Biology, 54:S29, 2018

Second Place

Acquired Thermotolerance and Heat Stress Memory in Chlamydomonas reinhardtii

High temperatures threat plants’ survival and reproduction in natural environments. The global warming will exacerbate heat-stress-induced damages in agricultural production. In order to mitigate adverse effects of high temperatures, especially those recurring heat stresses, plants develop the ability to cope with lethal high temperatures through sub-lethal temperatures priming. This ability is termed as acquired thermotolerance. The maintenance of acquired thermotolerance, sometimes lasting for several days, is referred as heat stress memory. The molecular basis and evolution of theromotolerance acquisition/memory have been studied in A. thaliana and rice, however, the mechanisms of action and genes involved remain largely unknown. Chlamydomonas reinhardtii, the unicellular green alga, is a powerful model organism for dissecting cellular mechanisms and gene functions in photosynthetic organisms. However, little is known about the acquired thermotolerance and heat stress memory in C. reinhardtii. We investigated the acquired thermotolerance and heat stress memory of C. reinhardtii in photobioreactors with precisely-controlled conditions (temperature, light, cell density and nutrients). Our results indicated that C. reinhardtii could develop acquired thermotolerance after priming at 35 °C for 90mins. In addition, we employed a genome-saturating, indexed mutant library of Chlamydomonas to identify genes involved in heat responses and identified a putative transcription factor with potential roles in heat stress memory. Its best Arabidopsis homologous gene has been reported to be involved in heat stress memory. We are working on to investigate the function of the gene in C. reinhardtii. This study demonstrated that algae could develop acquired thermotolerance. This will pave the way for us to further understand the molecular basis and mechanism of acquired thermotolerance and heat stress memory in Chlamydomonas. The information gained in Chlamydomonas can be transferred to other photosynthetic organisms, especially economic crops.