News porn the UCplant genomicspontier

ince recombinant DNA technologies were fied plant genes that are preferentially expressed Sfirst developed in the 1970s, scientists have in response to the silverleaf whitefly, but not the made dramatic advances in understanding how sweetpotato whitefly. The species-specific sig- plants germinate, grow, reproduce and interact nals are transported from silverleaf whitefly- with the environment. Much basic research in infested leaves to upper noninfested leaves to ac- plant molecular biology has focused on the tivate plant gene expression. Studies with the mechanisms of gene expression - how particu- silverleaf whitefly-induced gene SL W3 indicated lar genes are turned on or off - and on identify- that known defense and wound signals do not ing and cloning genes that bestow specific traits activate this gene. It appears that the silverleaf such as disease or pest resistance. Recently, sci- whitefly’s saliva may contain a novel elicitor for entists also have made great strides in sequenc- the systemic activation of SLW3 or that the ing plant genomes. Following are some recent silverleaf whitefly stimulates the squash plant to breakthroughs by UC researchers. generate this novel systemic signal. These find- Disease resistance. UC Davis plant pa- ings might lead to production of plants that thologist Pam Ronald has been a pioneer in de- would not silver when infested with the termining the genetic basis of bacterial blight silverleaf whitefly or might exhibit enhanced disease resistance in rice. In 1995, using plants defenses to phoem-feeding insects. native to West Africa and bred into cultivated Cold-tolerant crops. Also at UC Riverside, varieties at the International Rice Research Insti- geneticist Timothy Close and colleagues tute, her team isolated the Xu21 gene, the first Abdelbagi Ismail and Anthony Hall are making cloned gene known to confer disease resistance discoveries that could lead to more chilling- in rice. By cloning and transferring the gene into tolerant crops. In the Proceedings of the National other rice plants, the researchers made it pos- Academy of Sciences (Nov. 9,1999), they reported sible to create novel resistant varieties. By studying squash the identification of a gene in blackeye beans (a plants infested with More recently, as reported in Science (June 30, type of cowpea) that enables seeds to germinate silverleaf whitefly, 2000), Ronald and colleagues at the Salk Insti- and plants to emerge in cool soil. below, and plants tute for Biological Studies discovered that the Warm-season plants sown early in the grow- infested with the closely related Xu22 receptor domain that recognizes the bacte- ing season often fail if the soil is too cool. During sweetpotato whitefly, rial blight pathogen and signals the plant’s de- an unusually cool spring in 1995, the researchers which does not fense response can be swapped with another re- observed a link between a type of stress protein cause silvering, UC ceptor domain. The new protein now recognizes called a dehydrin and genetic variation in chill- Riverside scientists are learning more another molecule. Scientists may be able to engi- ing tolerance in cowpea plants. One cowpea about genes involved neer resistance to other pathogens by altering breeding line in crop damage. the receptor domain to recognize them. emerged more Silverleaf whitefly. UC researchers are eluci- successfully dating how plants respond to pests as well as than a closely pathogens. UC Riverside plant geneticist Linda related line. The Walling and collaborators Mien van de Ven, successful line Cynthia LeVesque and Tom Perring have re- contained a vealed how plants respond to the silverleaf large quantity whitefly. This insect is a devastating crop pest of a specific that vectors an array of debilitating viruses and dehydrin, which causes dramatic developmental disorders, such could not be de- as squash leaf/fruit silvering and tomato irregu- tected in seeds lar ripening, that impact the market value of of the other fruit. As reported in The Plant Cell (August lines. 2000), the investigators compared plant re- The research- sponses to the silverleaf whitefly and the closely ers identified related sweetpotato whitefly. They have identi- the gene that

CALIFORNIA AGRICULTURE, JULY-AUGUST 2000 11 encodes for biotechnology in the United States, led the expression of team that developed the world’s first the dehydrin transgenic barley. Other center achievements protein and have included cloning tobacco‘s N gene, a key found there is element in viral resistance, and the ACC syn- ._ indeed a ge- thase gene, which can be manipulated to con- 5 netic link be- trol fruit ripening. t- tween the Arabidopsis genome. In addition to probing 5I geneandthe particular genes, UC plant scientists are leading 2 trait. This major attempts to map the complete genomes of Timothy Close, UCR knowledge a variety of plant species. Genome sequencing geneticist, left, and gives scientists a new approach for improving and global gene expression analyses take plant UCR plant physiolo- cowpeas and perhaps other warm-season crops genetics research to a whole new level - that of gists and breeders such as soybean, cotton, corn, rice and sorghum. the entire organism - in the subfield of plant Abdelbagi ismail and Anthony Hall are Light responsiveness. UC Berkeley molecu- biotechnology known as genomics. PGEC’s working on a way to lar geneticist Peter Quail studies how plants Athanasios Theologis is collaborating with re- grow warm weather sense and respond to light stimuli. In recent searchers at Stanford University and the Univer- plants in cool soil. years his team has identified and cloned five sity of Pennsylvania in a landmark effort to se- molecules called phytochromes, plants‘ primary quence the Arabidopsis genome, which will allow photoreceptors, and is elucidating how they con- plant scientists worldwide to identify homolo- vert light stimuli into molecular signals that gous genes from important crops such as tomato switch on target genes. In Science (May 5,2000), and soybean. The researchers anticipate major the researchers reported that when phyto- breakthroughs in this work before the end of chromes are activated by light, they accumulate this year. in a cell’s nucleus and bind to promoters of Wheat genome. UC is a leading participant light-activated target genes, thereby regulating in the U.S. Wheat Genome Project, a $7.3 mil- their expression. In this way the phytochromes lion, 4-year project funded by the National Sci- act as light-activated molecular “switches,” ence Foundation with the goal of deciphering modifying gene expression. The scientists also the chromosomal location and biological func- identified a transcription factor, PIF3, that plays tion of all genes in the wheat genome. The a key role in this process. When activated by project, the first such effort for wheat, began in sunlight, phytochrome B binds to the PIF3 pro- September 1999. Calvin Qualset, director of the tein; this binding does not occur if the plant is UC Genetic Resources Conservation Program, kept in the dark. leads the project with 13 co-principal investiga- The work has major implications not only for tors from across the nation, three of them with basic science but for the potential to produce UC: Davis researchers Jan Dvorak and Jorge transgenic plants with altered responses to light. Dubcovsky and Riverside’s Close. For example, plants might be engineered to ger- Research in plant genetics requires multi- minate or flower at particular times controlled investigator, multi-institution collaborations, by growers. primarily due to the high equipment costs and Plant Gene Expression Center. Quail is af- efficiency of shared bioinformatics strategies filiated with the Plant Gene Expression Center and data analysis. A proposed institute could (PGEC) in Albany, one of the world’s leading re- become the focal point for this work throughout search institutions in plant molecular biology. the UC system. Established in 1984, the center represents a In July, the state legislature approved fund- unique arrangement between the USDA Agricul- ing for three California Institutes for Science and tural Research Service and UC. The USDA scien- Innovation to be based at UC. This fall an inter- tists at the center have adjunct appointments national panel of scientists and scholars will se- with the UC Berkeley department of plant and lect three institutes from six proposed, one of microbial biology, where they can teach and which is the California Institute in Agricultural train students. Genomics. The UC Riverside campus would As a UC Berkeley collaborative researcher at lead this institute, working in partnership with PGEC in the early l990s, Peggy Lemaux, one of the Berkeley and Davis campuses. the first two Cooperative Extension specialists in - ]ill Goetz

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