UC Davis plant biology professor William Lucas has been elected to the Academie de France, equivalent to the National Academy of Sciences of the USA.
Lucas has also been awarded the prestigious Interuniversity International Francqui Chair. The position, established by the Francqui Foundation, is one of the highest scientific honors awarded in Belgium. As holder of the Francqui chair, Lucas travels regularly to Belgium for lecturing and research.
The honors are in recognition of Lucas’ pioneering work in describing the local and long-distance "information superhighways" within plants.
Lucas says he could not describe how he felt when he heard he had been elected to the academy. "I’m elated by the whole thing," he says.
Last June, Lucas was formally inducted into the academy at a ceremony in Paris. "I was very impressed with the other individuals inducted—they were a wonderful group of international scholars," he says.
Lucas admires the broad outlook and intense style of French intellectual debate.
"They have a different style, and I kind of like that," he said. Lucas has overlapping interests with some French researchers, and often strong disagreements, too, which have stimulated further debate and helped to drive research.
Australian by birth, Lucas obtained his Ph.D. from the University of Adelaide and worked at the University of Toronto in Canada before arriving at UC Davis in 1977. It was at UC Davis that he began to study phloem, the network of highly specialized cellular tubes running through plants. Phloem forms the communication system that joins leaves, stems and roots into a single plant.
Lucas said that the direction of his research was changed dramatically by some failed experiments conducted during a sabbatical at the University of Göttingen, Germany, in 1984. He was trying to investigate the biophysical properties of phloem, but the experiments were compromised by the presence of plasmodesmata, small pores that connect the phloem to the cells in surrounding tissues.
At the time, it was thought that plasmodesmata formed simple pores between plant cells to allow the movement of essential nutrients.
Initially annoyed by the troublesome plasmodesmata, Lucas soon realized that this opened up a whole new area of research. He began to study plant viruses, and was able to demonstrate that these viruses make movement proteins that allow them to cross plasmodesmata and spread their nucleic acids –DNA or RNA–through a plant. The movement protein acts as a passport that lets the viral RNA cross the plasmodesmal checkpoint.
Lucas realized that these plant viruses were the key to understanding the plant’s own communication system, since they must have either acquired or copied these movement proteins from their hosts. His group provided the first evidence that specific plant proteins, some of them factors that control DNA transcription, have the capacity to move from cell to cell via plasmodesmata.
These discoveries led to the concept that, unlike animals, plants function as supracellular systems.
Normally, when a gene is turned on in one part of a plant, messenger RNA—mRNA—is made and translated into a protein within the same cell, leading to cell autonomous control. According to Lucas, cell-to-cell trafficking of proteins and mRNA allowed plant cells to talk to influence each other over processes in tissues and organs.
As these tissues are connected to the phloem by plasmodesmata, there was also the possibility that RNA molecules could be moving around the body of the plant. Lucas and his colleagues showed that this was indeed the case. This knowledge provided an explanation for systemic gene silencing, a process plants use to control virus infection.
Plants may use this system to regulate growth and development, says Lucas. Signals made of RNA and protein could move from mature leaves to young shoots, flowers and roots, telling each cell what is going on in other parts of the plant.
The discovery that nucleic acids can act as messengers that travel through a plant switching specific genes on or off has profound implications, Lucas said. "Studies on nucleic acid trafficking in plants are just going to explode," he said. That knowledge could lead to new ways to genetically modify plants, for example, to achieve higher yields, pest resistance or enhanced flavors or colors.
Examples of the silencing of specific genes by double-stranded RNA have recently been reported for fungi, insects such as the fruit fly Drosophila, the soil roundworm Caenorhabditis elegans and even mammals. By using this method to silence one gene or gene family at a time, scientists will be able to identify the role of each of the thousands of genes that make up plants and animals.
"This could likely turn out to be one of the most significant discoveries in terms of advancing the field of genomics," says Lucas. He is pleased that plant biologists led the way in these discoveries.
"Collectively, we’ve been working on this topic for a decade," he says.