Plant Ecosystem Engineering
Christer Jansson is the Director of Plant Sciences at PNNL and EMSL. He came to PNNL in September last year from LBNL where he was a Senior Staff Scientist and Bioenergy Program Lead at the Earth Sciences Division. Prior to joining LBNL in 2007, Christer was the Department Head at the Swedish Agricultural University in Uppsala, Sweden. Christer has a strong background and expertise in plant biochemistry, particularly in areas of photosynthesis, metabolism, and bioenergy applications, with 117 publications. He is the Lead PI and Co-PI for two DOE projects on Sorghum phenotyping funded by ARPA-E and BER, respectively. He is also the Lead PI for another ARPA-E funded project on biological conversion of methane to higher-value fuels, and was the Lead PI for a finished ARPA-E funded project on direct conversion of CO2 to fuels in tobacco leaves.
Making an ally from an enemy: The case of Citrus tristeza virus
Siddarame Gowda completed his undergraduate and graduate schooling in the University of Mysore, India and completed his Ph.D. in Biology at the University of Windsor, Ontario, Canada. After a brief period of Post-Doctoral fellowships at Columbia University Medical School in New York and University of Missouri Medical School at Columbia, Missouri he joined Dr. Robert Shepherd in the Department of Plant Pathology at University of Kentucky, Lexington, KY, as a Research Scientist, worked on Caulimoviruses and characterized the role of trans-activating protein in virus replication. Later he moved to Citrus Research and Education Center- University of Florida at Lake Alfred, Florida where he is still continuing. He is part of a research team headed by Dr. Bill Dawson, on the study of Biology of Citrus triseza virus, which is being used as a highly stable expression and gene silencing vector, and presently working with bacterial pathogen of citrus greening.
Citrus tristeza virus (CTV), is a phloem limited Closterovirus with ~19.2 kb plus-stranded RNA genome. The flexuous filamentous virions are approximately 2000nm long and 12nm in diameter are transmitted by aphids. The 5’ half of the genome encode replication related proteins, translated from the genomic RNA, while the 3’ end encodes nearly ten genes expressed by 3’ co- terminal sub-genomic RNAs which encode products involved in virion assembly, movement, vector specificity, silencing suppression and host-virus interactions. CTV has been developed into an expression vector capable of expressing foreign gene and has stably retained a foreign gene for more than a decade. In spite of encoding silencing suppressors, CTV has been engineered as Virus induced gene silencing (VIGS) vector capable of silencing citrus endogenous genes or green fluorescent protein (GFP) transgene. As a pathogen, CTV, induces quick decline of sweet orange on preferred sour orange root stocks and is not a major pathogen of citrus if replaced by other favoured root stocks. However, the Florida citrus industry is grappled by a more devastating bacterial citrus disease, Citrus greening disease (Huanglongbing, HLB). Since its first report in Florida in 2005, the disease has spread extensively and is estimated that nearly 80% of the standing citrus trees being infected. Both CTV and the causal agent of HLB, Candidatus Liberibacter asiaticus, are phloem limited pathogens transmitted by phloem feeding arthropod vectors, aphids and psyllids, respectively. We have shown that CTV can induce silencing of the endogenous genes of the phloem feeding psyllid vector. Thus, CTV vector could be used in a two-prong approach to individually or simultaneously express therapeutic antibacterial proteins against the HLB pathogen and silence the endogenous genes of the psyllid, Diaphorina citri Kuwayama, the vector of the HLB pathogen.
Qin Zhang, Ph.D.
Biological Systems Engineer
Director, Center for Precision & Automated Agricultural Systems
Agricultural machinery automation and agriculture automation.
Matt Whiting, Ph.D.
Genetic, horticultural and physiological components of consistent, sustainable, and profitable stone fruit production.
Doug Walsh, Ph.D.
Environmental and Agrichemical Education Specialist
Naidu Rayapati, Ph.D.
Interim Director, CPCNW
Virus diseases of horticultural, vegetable, and food crops. Virus diseases in international agriculture and capacity building in developing countries.
Troy Peters, Ph.D.
Biological Systems Engineer
Irrigation management for improved profitability and environmental benefits.
David James, Ph.D.
Conservation biological control, habitat restoration, sustainable pest management in irrigated horticulture. Butterfly biology and conservation.
In August 2015, Dr. Joan Davenport was inducted as fellow of the American Society for Horticultural Science. According to the article in the Good Fruit Grower, “Dr. Davenport’s research has focused on nutrient cycling through soil-plant systems in perennial fruit crops, with an emphasis on site-specific management of plant stress.” The full article regarding this achievement can be found at www.goodfruit.com/.