The majority of known plant resistance genes encode proteins with conserved nucleotidebinding sites and leucine-rich repeats (NBS-LRR). Degenerate primers based on conserved NBS-LRR motifs were used to amplify analogues of resistance genes fromthe dicot sugar beet. Along with a cDNA library screen, the PCR screen identified 27 genomic and 12 expressed NBS-LRR RGAs (nlRGAs) sugar beet clones. The clones were classified into three subfamilies based on nucleotide sequence identity. Sequence analyses suggested that point mutations, such as nucleotide substitutions and nsertion/deletions, are probably the primary source of diversity of sugar beet nlRGAs. A phylogenetic analysis revealed an ancestral relationship among sugar beet nlRGAs and resistance genes fromvarious angiospermspecies. One group appeared to share the same common ancestor as Prf, Rx, RPP8, and Mi, whereas the second group originated fromthe ancestral gene from which 12C1, Xa1, and Cre3 arose. The predicted protein products of the nlRGAs isolated in this study are all members of the non-TIR-type resistance gene subfamily and share strong sequence and structural similarities with non-TIR-type resistance proteins. No representatives of the TIR-type RGAs were detected either by PCR amplification using TIR typespecific primers or by in silico screening of more than 16,000 sugar beet ESTs. These findings suggest that TIR type of RGAs is absent fromthe sugar beet genome. The possible evolutionary loss of TIR type RGAs in the sugar beet is discussed.

A seed genetic model with embryo, endosperm, cytoplasmic and maternal effects and genotype

Mutation (substitution, deletion, insertion, etc.) in nucleotide acid causes the maximal sequence lengths of exact match (MALE) between paralogous members from a duplicate event to become shorter during evolution. In this work, MALE changes between members of 26 gene families from four representative species (Arabidopsis thaliana, Oryza sativa, Mus musculus and Homo sapiens) were investigated. Comparative study of paralogous' MALE and amino acid substitution rate (dA<0.5) indicated that a close relationship existed between them. The results suggested that MALE could be a sound evolutionary scale for the divergent time for paralogous genes during their early evolution. A reference table between MALE and divergent time for the four species was set up, which would be useful widely, for large-scale genome alignment and comparison. As an example, detection of large-scale duplication events of rice genome based on the table was illustrated.

Motivation: It was found that high accuracy splicing-site recognition of rice (Oryza sativa L.) DNA sequence is especially difficult. We described a new method for the splicing-site recognition of rice DNA sequences. Method: Based on the intron in eukaryotic organisms conforming to the principle of GT-AG, we used support vector machines (SVM) to predict the splicing sites. By machine learning, we built a model and used it to test the effect of the test data set of true and pseudo splicing sites. Results: The prediction accuracy we obtained was 87.53% at the true 5' end splicing site and 87.37% at the true 3' end splicing sites. The results suggested that the SVM approach could achieve higher accuracy than the previous approaches.

An ancient genome duplication (PPP1) that predates divergence of the cereals has recently been recognized. We report here another potentially older large-scale duplication (PPP2) event that predates monocot-dicot divergence in the genome of rice (Oryza sativa L.), as inferred from the age distribution of pairs of duplicate genes based on recent genome data for rice. Our results suggest that paleopolyploidy was widespread and played an important role in the evolution of rice.

An ideal test location with particular environmental conditions should generate a relatively large genotype

采用包括遗传主效应和基因型与环境互作效应的数量性状发育遗传模型和统计分析方法，分析了籼稻（Oryza sativa L.）稻米4个发育时期糙米重的两年资料。结果表明，除了三倍体胚乳和二倍体母体植株基因的加性和显性主效应以及细胞质主效应可以控制不同稻米发育时期的糙米重量外，基因型与环境互作效应也可明显影响不同发育时期糙米重量。基因加性主效应和加性×环境互作效应在整个稻米灌浆过程中起着主要作用，对糙米重的选择可以取得良好的改良效果。条件方差分量分析结果表明，胚乳和母体植株中控制糙米重表现的基因在多数稻米发育时期均有新的表达，且以稻米发育早期为主，开花后第1～7天是控制糙米重的基因表达最为活跃的时期，其次为开花后第8～14天。一些基因只在个别发育时期间断表达，这在净细胞质主效应和净细胞质×环境互作效应以及净显性主效应上表现得尤为明显。稻米不同发育时期的遗传效应预测值表明，V20和作5等亲本可以明显提高后代的糙米重量。

实地（杭州）调查了桑稻混种地区水稻花粉飘落到桑叶上的浓度，同时对转Bt基因水稻花粉向桑叶上飘飞程度进行了田间试验。20个采样点的调查结果显示，超过一半（54.5%）的桑叶检测到了水稻花粉，其浓度变化范围为13.3～199.0粒/cm2，平均浓度为92.9粒/cm2，与109.1粒/cm2（该浓度影响家蚕生长发育）持平（1=0.10，P>0.5）。不同桑稻距离（0～10m）的桑叶花粉浓度总体上是距离越近花粉浓度越高。将处于开花期的转基因Bt水稻和非转基因水稻植株（各3株）同时放入桑园中，然后观察水稻植株周边桑叶飘落上水稻花粉的浓度。两次试验采集的桑叶自然飘落的水稻花粉平均为3.8粒/cm2，这一结果证明水稻花粉可飘落到桑叶上，从而支持上述调查结果；试验同时证实转基因Bt水稻和非转基因水稻植株的花粉飘飞能力没有差异。以上研究结果表明，BT水稻在我国南方养蚕地区推广将可能对家蚕的生长发育造成负面影响。

如何分析转基因对植物遗传多样性的影响一直以来是一个难题。提出了一种所谓“人工杂交”的分析方法，即利用具有相同遗传背景的转基因及其野生型植物群体，分别与一组具有代表性的遗传对象进行有性杂交，通过考察它们后代主要性状分离变异状况来评估转基因导入对群体遗传性状的多样性的影响。作为一个实例，选用了由转基因水稻及其野生型组成的3对不同遗传群体，分别与7个具有代表性（如不同亚种、不同品种类型等）的水稻品种进行杂交，获得15对杂交组合，经杂种R自交获得F2种子，通过观测F2分离世代的主要性状分离状况，比较和统计转基因水稻群体及其野生型群体后代的性状分离程度。结果表明，提出的“人工杂交”技术路线是可行的，为全面和深入开展相关研究开辟了一个新途径。同时根据本研究利用这3对转基因水稻及其野生型群体的研究结果表明，在一些性状上转入的外源基因可以显著地增加种群内的遗传变异而在另外一些性状上却显著地减少了种群内的遗传变异，但尚不能得出或支持转基因植物可能对遗传多样性产生负面效应的结论。

重点介绍了在水稻基因组序列分析方面取得的几项最新研究结果。内容主要包括：水稻基因组被证实曾发生过全基因组倍增；水稻基因组大小变化的趋势；水稻籼粳亚种的分化时间比以前估计的100万年前要迟得多；对水稻基因产生Gc含量负梯度现象的解释。