SUMMARYDuring the course of evolution, mainly leguminous plants have acquired the ability to form de novo structures called root nodules. Recent studies on the autoregulation and hormonal controls of nodulation have identified key mechanisms and also indicated a possible link to other developmental processes, such as the formation of the shoot apical meristem (SAM). However, our understanding of nodulation is still limited by the low number of nodulation-related genes that have been identified. Here, we show that the induced mutation tricot (tco) can suppress the activity of spontaneous nodule formation 2, a gain-of-function mutation of the cytokinin receptor in Lotus japonicus. Our analyses of tco mutant plants demonstrate that TCO positively regulates rhizobial infection and nodule organogenesis. Defects in auxin regulation are also observed during nodule development in tco mutants. In addition to its role in nodulation, TCO is involved in the maintenance of the SAM. The TCO gene was isolated by a mapbased cloning approach and found to encode a putative glutamate carboxypeptidase with greatest similarity to Arabidopsis ALTERED MERISTEM PROGRAM 1, which is involved in cell proliferation in the SAM. Taken together, our analyses have not only identified a novel gene for regulation of nodule organogenesis but also provide significant additional evidence for a common genetic regulatory mechanism in nodulation and SAM formation. These new data will contribute further to our understanding of the evolution and genetic basis of nodulation.
1605 Background: The poor prognosis of cancer of unknown primary (CUP) patients is likely to improve with knowledge of the primary site. CUP patients form a diverse clinicopathological group; however, there remains doubt as CUP may indeed represent a unique clinical classification. Methods: We used the Ontario Cancer Registry to identify all patients diagnosed with cancer from January 2000 to December 2005. We linked these patients with the Canadian Institute of Health Information Same Day Surgery and Discharge Abstract Database to identify those who were initially diagnosed with a metastatic tumour. Information on clinical and pathological characteristics including age, gender, primary tumour site, histology, and second primary were available from the Ontario Cancer Registry. We stratified results according to primary tumour site and histology. Five-year survival data were available for all patients and were obtained from the Ontario Cancer Registry. Results: Of 52,619 patients diagnosed with metastatic tumour at the time of their initial cancer diagnosis, 4,866 (9.2%) patients were diagnosed with CUP and 47,753 (90.8%) patients were diagnosed with metastasis of known primary. The 5-year Kaplan-Meier estimate of CUP overall survival (OS) differed significantly with patients diagnosed with metastasis of known primary (median OS= 1.0 versus 10.4 months, respectively, log–rank test p<0.0001). In subgroup analyses, the 5-year OS of CUP patients with adenocarcinoma (n=1,389, median OS=1.83) was significantly worse when compared to metastatic adenocarcinoma of known primary (log-rank test p<0.0001). An identical result was obtained with CUP patients of undifferentiated histology (n=3,230). The 5-year OS of CUP patients with squamous cell carcinoma (n=247, median OS=18.5) did not differ significantly with those of other squamous cell carcinoma groups of known primary (log-rank test p>0.56). Conclusions: Although CUP patients as a whole have a poor prognosis compared to other metastatic patients of known primary, distinct subsets of CUP patients have similar prognosis. These data suggest that an intensive diagnostic approach for identification of the primary is not justified for all CUP patients.
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