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Alternaria black rot, Alternaria leaf spot of rough lemon, and Alternaria brown spot of tangerines are three major citrus Alternaria pathogens. Citrus could be considered as a molecular contact point for host-selective toxin (HST)-mediated co-evolution of these Alternaria pathogens and susceptibility in the field. ACR-toxin is an HST produced by the rough lemon pathotype, and the target site of the toxin was identified as rough lemon mitochondria. The biosynthetic gene cluster for ACR-toxin production is on the 1.5 Mb-chromosome of the rough lemon pathotype. Another gene cluster for ACT-toxin production is located on the 1.9 Mb-chromosome of the tangerine pathotype. These TOX genes shown to have a role in ACR- or ACT-toxin biosynthesis by using gene disruption and silencing. 相似文献
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Rieko Hatta Akihisa Shinjo Sheila Ruswandi Keiji Kitani Mikihiro Yamamoto Kazuya Akimitsu Takashi Tsuge 《Journal of General Plant Pathology》2006,72(4):210-219
The strawberry pathotype of Alternaria alternata produces host-specific AF-toxin and causes Alternaria black spot of strawberry. Previously, we isolated cosmid clones pcAFT-1
and pcAFT-2 from strain NAF8 of the strawberry pathotype that contain AF-toxin biosynthetic genes, named AFT genes. In a molecular characterization here of pcAFT-1 and pcAFT-2, 11 AFT genes and five transposon-like sequences, named TLS-S1 to TLS-S5, were detected. The nucleotide sequences of TLS-S1 and TLS-S4
share high homology, and their putative products have similarity to transposases of the hAT family transposons. Thus, TLS-S1 and TLS-S4 were renamed TLS-S1-1 and TLS-S1-2, respectively. Amino acid sequences deduced
from TLS-S2, TLS-S3, and TLS-S5 have similarity to transposases of the Fot1/Pogo family transposons, but they are significantly different. All five sequences have incomplete open reading frames (ORFs) for
transposases owing to deletions, termination codons, and/or frameshifts, indicating that they are inactivated elements. Analysis
of genomic distribution of these sequences revealed that they are specifically distributed on a 1.05-Mb chromosome of NAF8,
which has been identified as a conditionally dispensable (CD) chromosome encoding AFT genes. The presence of three, four, and three copies of TLS-S1, TLS-S2, and TLS-S3, respectively, and a single copy of TLS-S5
on the CD chromosome were estimated by DNA gel blot analysis. The remaining copy of TLS-S1 and the three copies of TLS-S2
were isolated and identified to also encode incomplete ORFs. Thus, it appears that all copies of the transposon-like sequences
identified are inactivated elements (fossils) unique to the CD chromosome in the genome of the strawberry pathotype.
The nucleotide sequence data reported are available in the DDBJ/EMBL/GenBank databases under the accession numbers AB236733
(TLS-S1-1), AB236734 (TLS-S1-2), AB236735 (TLS-S1-3), AB236736 (TLS-S2-1), AB236737 (TLS-S2-2), AB236738 (TLS-S3), and AB236739
(TLS-S5) 相似文献
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Atlantic salmon with body weight of 493 g were fed 6 graded levels of methionine in diets based on plant proteins for a period of 85 days with the aim to test whether methionine intake affected growth, nutrient accretion and hepatic sulphur metabolism. A negative control based on a mixture of plant proteins with low fish meal inclusion (5%) containing 1.64 g methionine 16 g− 1 N was added five levels of dl-methionine resulting in dose levels from 1.64 to 2.98 g methionine 16 g− 1 N. A control feed based on fish meal (26%) and plant proteins (44.9%) containing 2.30 g methionine 16 g− 1 N was used as a control for growth performance. Feed intake and thus growth was generally lower in fish fed the plant protein based diets, while digestibility of amino acids was higher in fish fed the test diets as compared to those fed the fish meal based positive control diet. However, no significant differences in either feed intake or growth were present in fish fed either of the test diets containing graded levels of methionine. Neither carcass protein or lipid retention was affected by methionine intake as confirmed by the unaffected mRNA levels of growth hormone-insulin-like growth factor in hepatic and muscle tissues. Hepatic size as well as transsulfuration was significantly affected by methionine intake. Thus it is concluded that nutrient accretion was not the main effect of methionine intake (ranging from 35 to 90 mg fish− 1 day− 1). Rather methionine is essential to secure high synthesis of activated methyl groups for methylation reactions ensuring a healthy fish not developing increased liver size. Intakes exceeding 60 to 70 mg methionine daily in the fast growing seawater period results in increased transsulfuration analysed as increased hepatic taurine production keeping the hepatic free methionine constant at all intakes. 相似文献
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Alternaria alternata includes seven pathogenic variants, called pathotypes, which produce host-selective toxins (HSTs) as determinant factors for pathogenicity. The gene clusters for HST biosynthesis were identified from six pathotypes (Japanese pear, strawberry, tangerine, apple, tomato and rough lemon) and were found to reside on small chromosomes of <2.0 Mb in most strains tested. We isolated mutants lacking the small chromosomes from the strawberry, apple and tomato pathotypes and showed that the small chromosomes are dispensable for growth. In this review, we summarize our current understanding of the evolution of pathogenicity controlled by small, dispensable chromosomes in Alternaria alternata pathogens. 相似文献
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