Biotechnology Seminar

Alana Clegg will present a special seminar titled, Subcellular Localization of the Tobacco MAPKs SIPK and WIPK in Response to Pathogen attack by Harpin and Megaspermin on Wed. August 11, 2004 at 12 noon in the Plant Science Lounge, MacMillan 318D. All are welcome, graduate students in Plant Science and all investigators and associates of the UBC Centre for Plant Research are encouraged to attend.

Following is the abstract for the seminar:

"Plants effect intracellular changes in response to a variety of external stimuli.In particular, plants are equipped with a variety of mechanisms to deal with direct stresses. The hypersensitive response (HR) is an early defense response which restricts growth of a pathogen by necrosis and cell death. An accumulation of pathogenesis related (PR) gene transcripts, and a subsequent secondary immunity to attacks from a broad range of pathogens is also present in the HR (Ryals et al., 1994).
Harpin, a bacterial elicitor from the bean halo-blight pathogen Pseudomonas syringae pv phaseolicola, and megaspermin, a fungal elicitor secreted by Phythophtora megasperma H20, are known to elicit a HR in tobacco and induce activation of a 48 kDa protein and a 46 kDa protein that have been identified as Salicylic Acid Induced Protein Kinase (SIPK), and Wound Induced Protein Kinase (WIPK) respectively. These two kinases are signaling proteins belonging to the mitogen activated protein kinase (MAPK) family, a protein class that is involved in a variety of plant signaling pathways.
Previous work by has shown that transient over-expression of SIPK causes lesion formation in tobacco leaves, suggesting a possible role for SIPK in regulating tobacco HR signaling. Extracellular Regulated Kinase (ERK) a mammalian homologue to SIPK and WIPK, has been shown to localize to different parts of the cell in response to a variety of stresses. In yeast, the specific subcellular localization of ERK elicits different cellular responses (Leonormand et al, 1993; Zhu et al., 2003; Shapiro et al., 1998). The objective of this study was to determine the subcellular localization of the tobacco MAPK SIPK in response to challenge by harpin and megaspermin.
Using both SIPK-GFP proteins and in situ immunolabelling of SIPK and WIPK, it was determined that the tobacco MAPKs had a general cytoplasmic, and nuclear localization. Upon challenge with harpin and/or megaspermin the phosphorylated forms of SIPK and/or WIPK moved predominantly to the nucleus. In the case of induced tobacco cell culture, there was a strong nucleolar localization within the nucleus. These results are consistent with the model that activation of ERK-homologues by intracellular effectors leads to translocation of the activated MAPK from the cytoplasm to the nucleus, most likely to effect transcriptional regulation of stress related genes."

Posted by Eric La Fountaine at 10:23 AM on August 5, 2004