Multiple copies of <Emphasis Type="Italic">AMT2</Emphasis> are prerequisite for the apple pathotype of <Emphasis Type="Italic">Alternaria alternata</Emphasis> to produce enough AM-toxin for expressing pathogenicity

The apple pathotype of Alternaria alternata produces the cyclic depsipeptide AM-toxin and causes Alternaria blotch of apple. Previously, we cloned AMT2 from the apple pathotype as an orthologue of AFTS1, which is required for biosynthesis of the decatrienoic acid ester AF-toxin I of the strawberry pathotype. These genes were predicted to encode aldo-keto reductases involved in biosynthesis of a common precursor, 2-hydroxy-isovaleric acid, of AF-toxin I and AM-toxin. In this study, we analyzed the function of AMT2 in AM-toxin biosynthesis in the apple pathotype. DNA gel blot analysis of the apple pathotype strain IFO8984 with five restriction enzymes suggested that this strain has a single copy of AMT2 in the genome. However, gene disruption experiments showed that IFO8984 probably has three copies of AMT2. We made mutants having one or two copies of AMT2 disrupted. The single-copy mutants produced less AM-toxin than did the wild type and were still as pathogenic as the wild type. The two-copy mutants produced trace or undetectable amounts of AM-toxin and were markedly reduced in pathogenicity. Thus, AMT2 was verified to be required for AM-toxin biosynthesis and hence pathogenicity. The fact that the two-copy mutants have a remaining copy of AMT2 suggests that multiple copies of AMT2 are prerequisite for the pathogen to produce enough AM-toxin for full pathogenicity.     

Colonization of the vegetative stage of rice plants by the false smut fungus Villosiclava virens,as revealed by a combination of species‐specific detection methods

Rice false smut disease caused by the ascomycete fungus Villosiclava virens (Clavicipitaceae) reduces rice yield worldwide. It invades rice panicles and forms dark‐green false smut balls composed of thick‐walled conidia. Although the infection process during the booting stage is well studied, its infection route before this is unclear. It was hypothesized that the thick‐walled conidia in soil penetrate rice roots, and the fungus latently colonizes roots and tiller buds at the vegetative stage. This hypothesis was tested using species‐specific detection methods. First, real‐time PCR with species‐specific primers and probe was used to estimate thick‐walled conidial number in the paddy field soil. Secondly, nested PCR with species‐specific primers showed that fungal DNA was detected in roots and shoot apices of rice plants in the vegetative stage. Thirdly, colourimetric in situ hybridization with a species‐specific oligonucleotide probe targeting 18S rRNA suggested that sparse mycelia or tightly condensed mycelia were present on the external surface of tiller buds enveloped by juvenile leaf sheaths at the vegetative stage. Thin hyphae were found around leaf axils at the surface of elongated stems at the heading stage, and the fungal hyphae grew in the rice root tissues. In addition, it was demonstrated that eGFP‐tagged transformants of the fungus invaded rice roots and colonized the surface of roots and leaf sheaths under artificial conditions.     

The DNA damage signal transducer ortholog <Emphasis Type="Italic">Mop53BP1</Emphasis> is required for proper appressorium differentiation and pathogenicity in <Emphasis Type="Italic">Pyricularia oryzae</Emphasis>

Appressorium differentiation, one of the most important steps in pathogenesis by the rice blast fungus, Pyricularia oryzae, is strongly coordinated with the cell cycle. In this study, we identified an ortholog gene of 53BP1, which encodes a signal transducer protein that participates in G2-M cell cycle checkpoint in higher eukaryotes, in the genome of P. oryzae and characterized the phenotype of deletion and overexpression mutants. Deletion mutants showed no significant deficiency in vegetative growth compared to wild-type and complemented strains, even on the media containing DNA-damaging agents. However, these null mutants had abnormal appressoria and formed more appressoria per conidium than in the wild type and were unable to penetrate the epidermis of rice leaves. eGFP-fused Mop53BP1 and qRT-PCR analyses revealed that Mop53BP1 is expressed during the first hours of appressorium formation. In addition, in overexpression mutants, Mop53BP1 localized to nuclei during all stages of appressorium maturation and penetration, and the mutants were resistant to the microtubule inhibitor benomyl, suggesting that Mop53BP1 is nuclear protein and may have some role related to microtubules.     

SONOGRAPHIC APPEARANCE OF UREMIC GASTROPATHY IN FOUR DOGS

Gastrointestinal signs are common in dogs with uremia. Structural changes in the stomach associated with uremia in dogs include ulceration, edema, necrosis, gastric wall thickening, submucosal arteriopathy, and mineralization of the gastric mucosa and submucosa. Upon ultrasonographic evaluation of the abdomen in four dogs with severe uremia due to chronic renal disease, a thickened gastric wall, thickened rugal folds, and a hyperechoic line at the mucosal-luminal interface due to mineralization of the gastric mucosa were found. Ultrasonography was more sensitive than survey radiography for the identification of gastric lesions associated with uremia in these dogs.     

Immunohistochemical study of gastroenteropancreatic endocrine cells of the herbivorous Japanese field vole, Microtus montebelli

The gastroenteropancreatic (GEP) endocrine cells of the Japanese field vole were studied immunohistochemically. Somatostatin-, 5-hydroxytryptamine-, glicentin-, glucagon-, bovine pancreatic polypeptide-, gastrin-, gastric inhibitory polypeptide-, cholecystokinin-, substance P-, secretin-, neurotensin- and insulin-immunoreactive cells were revealed. The characteristic findings of the regional distribution and relative frequency of these immunoreactive cells in the GEP system of the vole were as follows. Somatostatin-immunoreactive cells were more numerous in the oxyntic glands than in the pyloric glands. Some somatostatin-immunoreactive cells were found in small clusters in the oxyntic glands. Gastrin-immunoreactive cells were detected not only in the pyloric glands and small intestine but also in the caecum and spiral colon. Gastric inhibitory polypeptide-immunoreactive cells were also detected in the pyloric glands and no motilin-immunoreactive cell was found in the gastroenteropancreatic system.     

便携式测定仪在测定叶片衰老过程中氮和叶绿素含量上的应用

选取哈尔滨地区本地植物华北紫丁香和山槐,以及华北引进种紫穗槐为研究材料,于2003年秋季对3种植物叶片从夏末叶片盛期到秋末叶片脱水变干脱落全过程进行了连续测定.结果表明:1)2种仪器对于表征单位叶面积上叶绿素和N含量的有效性明显高于表征单位鲜质量上叶绿素和N含量.2)尽管PPW-3000和SPAD-502对于表征单位叶面积N含量和各种叶绿素含量具有一定的普适性(R2=0.51～0.65),但不能有效表征不同植物的种间差异性.因此,使用2种便携式测定仪准确估计N和叶绿素含量需要首先确定每种植物的标准校正曲线.3)当表征同一种植物不同生长时期叶绿素和N含量变化时,2种仪器都适用于表征本地种华北紫丁香和山槐叶片衰老过程的变化(R2＞0.82);而对于外地引进种紫穗槐,叶片衰老脱水过程中叶绿素并未同时分解,表征效果欠佳(R2＜0.66),甚至相关性不显著.可见,便携式仪器更适用于适应本地气候的正常衰老种的相关测定.4)2种仪器比较而言,PPW-3000对于表征叶片N含量变化,尤其是对于叶片衰老脱水过程叶绿素并未同时分解的叶片(如紫穗槐),效果较SPAD-502好;而对于叶片衰老过程中叶绿素同时降解的叶片(如华北紫丁香和山槐),2种仪器效果没有明显区别.     

Chemical components of hardwood barks stripped by the alien squirrel Callosciurus erythraeus in Japan

The Pallas squirrel (Callosciurus erythraeus; common name in Japan: Formosan squirrel) was introduced in the 1950s and has established populations throughout southeastern Kanagawa Prefecture, Japan. Some tree species in natural forests, parks, and gardens in residential areas have been intensively debarked by the squirrels, especially in winter and spring. The amounts of chemical components, such as polyphenols, resins, flavanols, and sugars, in the bark were compared among species and individual trees collected in the forest of Yokohama Nature Sanctuary. Interspecific differences in the extent of stripping were not related to the amounts of the four chemical components. For individual trees, the bark with feeding scars tended to contain more sugar than that without scars.     

Acclimation of shoot and needle morphology and photosynthesis of two Picea species to differences in soil nutrient availability

To investigate morphological acclimation to differences in nutrient availability, we compared shoot and needle morphology of Picea glehnii (Friedr. Schmidt) M. T. Mast. and Picea jezoensis (Siebold & Zucc.) Carrière trees growing on nutrient-poor volcanic ash and nutrient-rich, brown forest soil. Trees of both species were shorter and had more open canopies when growing on volcanic ash than when growing on brown forest soil. Nutrient-poor conditions limited height growth less in P. glehnii than in P. jezoensis. In both species, trees growing on volcanic ash had shorter annual increments in the previous year and more needles per shoot length and, hence, a smaller shoot silhouette area (SSA) relative to needle dry mass (NDM) than trees growing on brown forest soil. Soil type had less effect on shoot projected needle area (PNA). Total needle area (TNA) of P. glehnii shoots was similar between soil types, whereas TNA of P. jezoensis was lower in trees growing on volcanic ash than in trees growing on brown forest soil. For both species, low SSA in response to nutrient-poor conditions resulted in low shoot SSA/PNA ratios, indicating high within-shoot self-shading. Shoot SSA/TNA of P. glehnii was lower in trees growing on volcanic ash than in trees growing on brown forest soil, indicating that needles were sun-acclimated. In contrast, shoot SSA/TNA of P. jezoensis was higher in trees growing on volcanic ash than in trees growing on brown forest soil. The contrasting response of TNA to low nutrient availability was associated with species-specific differences in needle morphology. Needles of P. glehnii growing on volcanic ash were slightly shorter, wider, thicker and heavier than those of trees growing on brown forest soil, indicating morphological acclimation to high irradiance. Needles of P. jezoensis growing on volcanic ash were shorter than those of trees growing on brown forest soil, but did not show morphological acclimation to high irradiance in width, thickness or mass. For both species, nutrient-poor conditions decreased maximum photosynthetic rate (Amax) per NDM. However, when expressed per PNA, the decrease in Amax was reduced, and when expressed per SSA, Amax was higher in trees growing on volcanic ash than in trees growing on brown forest soil. On volcanic ash, Amax per NDM was lower for P. glehnii than for P. jezoensis. However, morphological changes at the shoot and needle levels reversed this trend when Amax was expressed per SSA or per PNA. The species-specific differences in morphological response to differences in soil nutrient availability suggest that P. glehnii is more tolerant of nutrient-poor conditions, whereas P. jezoensis is better at exploiting nutrient-rich soils.