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Variance or complete loss of the avirulence gene (Avr) enables the pathogen to escape resistance protein (R) recognition. The field resistance effectiveness of the R gene is determined by its corresponding Avr gene in field isolates. To effectively deploy the rice blast R gene Pi54, the distribution, variation and evolution of the corresponding Avr gene, AvrPi54, were determined through PCR amplification, pathogenicity assay, gene sequences and evolutionary analysis. Among 451 Pyricularia isolates from rice and non-rice hosts, including Oryza rufipogon, Digitaria sanguinalis, Eleusine coracana, E. indica and Musa sp. in Yunnan province, the PCR amplification result showed that AvrPi54 alleles existed among 218 (48.3%) isolates including rice isolates, O. rufipogon isolates and E. coracana isolates. Pathogenicity assay showed that 336 (74.5%) isolates were avirulent to Tetep (holding Pi54). Five AvrPi54 haplotypes were identified among 142 isolates through the gene sequence. These haplotypes were determined to be avirulent to Pi54 through pathogenicity assay. Four novel haplotypes (H2 to H5) of the AvrPi54 gene would provide new target sites for rice blast control. Haplotype diversity analysis indicated that there existed a lower genetic diversity of AvrPi54 for P. oryzae populations (five haplotypes, Hd = 0.127, π = 2.9 × 10−4) in this study. Neutrality tests showed that AvrPi54's genetic variation was affected by purified selection. Haplotype network and phylogeny analysis showed that H1 was an ancestral haplotype and was widely distributed in rice isolates and O. rufipogon isolates, while H5 diverged early and evolved independently. These results indicate that the gene evolves slowly and stably and is a comparatively conserved Avr gene. [ABSTRACT FROM AUTHOR]

Abstract: FR429 is an ellagitannin with a potential antitumor activity, isolated and purified from Polygonum capitatum Buch.-Ham.ex D.Don, which is a traditional Miao-nationality herbal medicine in Guizhou and Yunnan of China. Our preliminary result of pharmacology study has indicated that the antitumor activity of FR429. However, the metabolism of FR429 has not been reported yet. In this study, LC–ion trap-time of flight mass spectrometry (LC–IT-TOF/MS) was used to characterize unpredictable metabolites of FR429 biotransformed by intestinal bacteria in vitro. Total thirteen metabolites were detected and characterized via comparisons of their accurate molecular masses and fragment ions of each MS n stage with those of the parent drug, and four of them were also elucidated by NMR. The results demonstrated that FR429 could be transformed by intestinal bacteria in vitro, mainly via hydrolysis and reduction reaction. This work provided a basis for the further study on the biotansformation of FR429 in vivo. [Copyright &y& Elsevier]