玉米自交系B73全基因组NBS类型抗病基因分析

核苷酸结合位点(NBS)类型抗病基因是植物抗病基因中最大的一个类别，也是近年来植物抗病分子育种研究的一大热点。本研究对玉米自交系B73全基因组中含有NBS结构的候选抗病基因进行了基因总数、类型、系统进化关系等分析。在B73全基因组中含有165个NBS结构的基因，远远少于水稻中的同类基因，按照N-端结构和亮氨酸富集区(LRR)结构, 将其分为153个标准结构和12个非标准结构NBS基因。其中，标准结构基因又分为CC-NBS-LRR、CC-NBS、NBS、NBS-NBS、 NBS-LRR、NBS-NBS-LRR、NBS-X、X-NBS等8个类型。系统进化树分析表明，NBS类型抗病基因存在明显的两大分支，与水稻的星状发散型分布有很大差异。通过基因家族分析，还发现了玉米NBS类型基因的复制现象，但发生复制的基因比例低于水稻，可能是造成玉米NBS抗病基因数目较少的原因之一。

Genome-Wide Analysis of NBS-Encoding Disease Resistance Genes in Maize Inbred Line B73

Nucleotide-binding site (NBS) disease resistance gene is a largest category in plant disease resistance genes, which is a focus in recent studies on molecular breeding of plant disease resistance. Using maize (Zea mays L.) inbred line B73, the complete set of disease resistance candidate genes that encode NBS was identified in the genome. The putative NBS genes were characterized with respect to structural diversity, phylogenetic relationships and so on. One hundred and sixty-five NBS-coding sequences were identified into two types: nonregular (12) and regular NBS genes (153). The amount of NBS genesis much smaller in maize than in japonica rice (Oryza sativa L.). The 153 regular NBS genes were categorized into eight classes, including CC-NBS-LRR, CC-NBS, NBS, NBS-NBS, NBS-LRR, NBS-NBS-LRR, NBS-X, and X-NBS, according to N-terminal motif and leucine-rich repeat (LRR) domains motif. The 165 NBS genes showed two remarkable branches in the phylogenetic tree, differing from the radiation structure in japonica rice. Gene duplication event was observed based on gene family analysis of the NBS disease-resistance genes in maize; however, the ratio of gene duplication was smaller than that in rice. This might be one of the reasons for less NBS disease-resistance genes in maize than in rice.