A genome‐wide survey reveals abundant rice blast R genes in resistant cultivars

Plant resistance genes (R genes) harbor tremendous allelic diversity, constituting a robust immune system effective against microbial pathogens. Nevertheless, few functional R genes have been identified for even the best‐studied pathosystems. Does this limited repertoire reflect specificity, with most R genes having been defeated by former pests, or do plants harbor a rich diversity of functional R genes, the composite behavior of which is yet to be characterized? Here, we survey 332 NBS‐LRR genes cloned from five resistant Oryza sativa (rice) cultivars for their ability to confer recognition of 12 rice blast isolates when transformed into susceptible cultivars. Our survey reveals that 48.5% of the 132 NBS‐LRR loci tested contain functional rice blast R genes, with most R genes deriving from multi‐copy clades containing especially diversified loci. Each R gene recognized, on average, 2.42 of the 12 isolates screened. The abundant R genes identified in resistant genomes provide extraordinary redundancy in the ability of host genotypes to recognize particular isolates. If the same is true for other pathogens, many extant NBS‐LRR genes retain functionality. Our success at identifying rice blast R genes also validates a highly efficient cloning and screening strategy.     

Effect of jasmonic acid on endogenous gibberellins and abscisic acid in rice under NaCl stress

Content of endogenous abscisic acid (ABA) increased in rice plants under salt stress. Pre- or post-treatment by jasmonic acid (JA) mostly further increased ABA content. In the presence of salt stress also content of gibberellins (GAs) mostly increased more after treatment by JA. Endogenous content of bioactive GA₁ was higher in post-treatment by JA than in pre-treatment by JA.This study was supported by the Korea Science and Engineering Foundation (2000-2-20100-001-3)     

水稻红莲型细胞质雄性不育系小孢子不同发育时期花药总蛋白质比较分析

采用双向凝胶电泳对水稻红莲型细胞质雄性不育的不育系小孢子发育单核期和二核期花药总蛋白进行了分离,通过银染显色,获得了分辨率和重复性较好的双向电泳图谱,且单核期和二核期花药总蛋白质在双向电泳胶上分布的图谱十分相似。PDQuest 2DE图像分析软件在等电点(pI)3.0~10.0、分子量(M.W.)9.0~98.0 kD之间可识别约1 800个蛋白质点。比较分析发现单核期和二核期花药中共有241个差异表达的蛋白质点,其中仅在单核期中表达的点数为125,仅在二核期中表达的为13点;表现为表达量差异的105点,其中在二核期表达下调的点数为70点,表达上调的为33点。还对蛋白质点集中的区域(pI 4.5~8.0,M.W.25.0~70.0 kD)中的41个差异蛋白质点进行了分子量和等电点分析。     

灌浆期气温与源库强度对稻米品质的影响及其生理分析

利用自然条件下的早、晚季种植作为温度处理,选择米质低、中、优等级的6个水稻品种（组合）作为供试材料,研究了早、晚季种植下的稻米品质、淀粉分支酶活性变化,以及温度处理间的差异.结果表明,在籽粒灌浆初期,高温环境下灌浆充实的籽粒,其稻米的垩白增加、透明度变差、整精米率下降,对出糙率及精米率没有明显影响.与早季种植的稻米相比,晚季种植稻米的胶稠度、整精米率、透明度增加.早、晚季种植对稻米直链淀粉含量、蛋白质含量等没有显著影响.剪叶限源处理显著降低稻米质量,疏粒减库处理显著提高稻米品质.     

Micronutrients’ accumulation in rice after supplemental UV-B irradiation

UV-B-mediated effects in Oryza sativa L. are studied considering micronutrients’ accumulation and the photosynthetic performance. UV-B-irradiated rice leaves showed increasing membrane permeability and an inhibition of Fe accumulation linked to an antagonistic interaction with Mn. An increasing passive Cu uptake is also pointed, whereas Zn contents are associated with a higher root acidification capacity. In UV-B-irradiated leaves, photosynthetic pigments and the rates of the light reactions decreased significantly between the 15th and 28th day after germination. In the leaves grown after UV-B exposure, the electron transport rates coupled to photosystems II and II plus I increased significantly between the 21st and 28th day, whereas the Mehler reactions increased continuously from the 21st day onward. It is concluded that during vegetative growth the nutrient status is mostly linked to the inhibition of roots’ acidification capacity, but after UV-B exposure micronutrients’ accumulation favors this genotype recovery, shielding the photosynthetic light reactions.     

PFGE analysis of the rice genome: estimation of fragment sizes,organization of repetitive sequences and relationships between genetic and physical distances

Pulsed-field gel electrophoresis (PFGE) has been applied to analyze the rice nuclear genome. Probing 56 RFLP probes selected from the 12 rice chromosomes to PFGE blots of nine rare-cutting restriction enzymes revealed that there are relatively high numbers of rare-cutting restriction sites in the rice genome. The average sizes of restriction fragments detected by single-copy probes are smaller than 200 kb for all of the rare-cutting restriction enzymes examined. Sizes of fragments detected by repetitive probes are variable, depending on the probes analyzed. By using PFGE, a tandemly repeated sequence, Os48, was found to be tightly linked to telomeric tandem repeats but not physically linked to r5s genes with which sequence homology had been observed. Relationships between genetic and physical distances have been established for three different chromosomal segments. In these regions 1 cm corresponds to ca. 260 kb on average. Analysis of a cluster of RFLP markers on chromosome 3 revealed that genetically clustered RFLP markers are also physically closely linked, suggesting that clustering of genetic markers may result in part from uneven distribution of single-copy sequences.     

石刁柏花粉离体培养及再生植株的研究

对石刁柏花粉粒进行离体培养,用ＭＳ基本培养基,激素ＮＡＡ０．５ｐｐｍ／Ｌ,花粉粒开始启动,形成细胞团,产生了愈伤组织,经去分化而形成单倍体植株（ｎ＝１０）。同时对花药壁,植物激素在花粉粒发育中的作用及再生植物染色体倍性问题进行研究。本文为选育超雄株在理论与实践方面均进行了探讨。     

运用致病毒素筛选抗稻瘟病细胞突变体

本文研究报道了抗稻瘟病细胞突变体筛选方法、程序与结果,并对有关问题进行了讨论。毒素对水稻成熟胚愈伤组织的诱导与分化有明显的抑制作用,抑制程度随毒素浓度提高和处理时间延长而加强,但抗感品种之间差异显著。以含毒素的诱导培养基或诱导与分化培养基均含毒素的筛选处理效果较好,而且简便易行。5年来接种筛选了29个品种25000多个外植体,在已鉴定的349个R_1个体中,有183株表现抗病。经多次接种鉴定与选择,已获得12个高抗稻瘟病的株系和1个抗病丰产品系,并对部分抗病突变体的抗性基因进行了遗传分析。