On the Defense|
On the Defense: Conserved Features of Plant Innate Immunity
The innate immune response is the body's first line of defense against pathogen infection. In the June 15th issue of G&D, Dr. Xin Li (University of British Columbia) and colleagues report that three proteins work together in the MOS4-associated complex (MAC) to execute innate immunity in the mustard weed, Arabidopsis.
Dr. Li and colleagues study a plant autoimmune model in which a mutation in one immune receptor, SNC1, causes constitutive activation of the plant's immune response. Dr. Li's group found that 3 key downstream effectors of the SNC1 pathway – MOS4, AtCDC5 and PRL1 – are homologous to components of the human spliceosome-associated nineteen complex (NTC). The researchers speculate that the evolutionarily conserved NTC may also play a role in animal innate immunity.
"Our work is further evidence that the little plant Arabidopsis remains a very robust genetic tool for dissecting processes in multicellular eukaryotes, with relevance to the realm of human biology. To our knowledge, this is the first placement of the NTC into a known signaling pathway in any organism. We are continuing to find commonality between animal and plant innate immunity at the level of both receptors and signalling intermediates; the complex we describe, essential for plant innate immunity, may be another example of this."
Banding Together: RAS signaling of circadian output
In the June 15th issue of G&D, Drs. Jay Dunlap and Jennifer Loros, with colleagues at Dartmouth Medical School, have finally cloned the band gene, and have found that it is an allele of ras-1.
This finding posits RAS signaling as a key mediator of circadian output.
The fungus Neurospora crassa is one of the best studied laboratory systems for circadian rhythms. However, over the past 50 years, almost all of the work done on Neurospora has used laboratory strains carrying the band mutation, because it enables researchers to visualize the fungus' daily circadian growth cycles. Research on Neurospora using this strain has contributed to understanding the basis of jet lag as well as some affective disorders.
While the band mutation has facilitated Neurospora clock observation, researchers are only now realizing what protein is encoded by the band gene, and how the subtle nature of the disruption in the band gene affects Neurospora circadian rhythms.
The Dartmouth team demonstrate that the band mutation is a dominant point mutation in ras-1 that causes a slight increase in GTP exchange, and therefore slightly higher activity levels. Says Dunlap, "Understanding the molecular nature of band makes us all look at output from the circadian clock in a different and clearer way. It's been a long time coming."
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