Iqbal M J, Yaegashi S, Njiti V N, Ahsan R, Cryder K L, Lightfoot D A
Center for Excellence in Soybean Research, Teaching and Outreach, Department of Plant, Soil and General Agriculture, Southern Illinois University at Carbondale, Carbondale, IL 62901, USA.
Mol Genet Genomics. 2002 Nov;268(3):407-17. doi: 10.1007/s00438-002-0762-6. Epub 2002 Oct 17.
Soybean Sudden Death Syndrome (SDS) is caused by Fusarium solani f.sp. glycines (Fsg). Six quantitative trait loci (QTLs), each conferring partial resistance to SDS, have been discovered in an Essex x Forrest recombinant inbred line (RIL) population, but their mode of action is not clear. This study aimed to identify genes (ESTs) whose mRNA transcripts were altered in abundance in soybean roots following inoculation of Fsg. Roots of the soybean variety Forrest (four resistance alleles) were inoculated with Fsg, and 14 days later RNA sequences that were differentially expressed relative to uninoculated roots were enriched using suppression subtraction and differential display. The abundance of these RNAs was quantified in inoculated and non-inoculated roots by macroarray hybridizations. A unigene set of 135 ESTs was identified and used in a further macroarray analysis. The abundance of 28 cDNA fragments was increased more than two-fold in inoculated compared to uninoculated roots of RIL 23 (six resistance alleles). In Forrest and Essex (two resistance alleles), the level of only one mRNA was increased two-fold in inoculated roots compared to the uninoculated roots. In Essex most of the mRNAs analyzed decreased in abundance (61/135 showed a two-fold decrease), while in Forrest most mRNA abundances did not change. Among the 28 cDNAs that revealed a two-fold or higher increase in mRNA abundance in RIL 23, 14% code for proteins known to be involved in plant defense, 21% in metabolism, 14% in cell structure and 4% in transport. Unannotated ESTs accounted for 43% of the genes, and 4% of the sequences were previously unknown. The plant defense-related genes that showed a differential response to Fsg inoculation suggested a role for the phenylproponoid pathway in soybean defense against Fsg. In Essex, genes involved in plant defense, cell wall synthesis, ethylene synthesis and metabolism were expressed at lower levels in inoculated roots. The difference in response between the 2-, 4- and 6-gene pyramids suggests that QTLs for SDS resistance serve to delay symptoms or confer resistance by maintaining or increasing the expression of specific genes after inoculation/infection.
大豆猝死综合征（SDS）由大豆镰刀菌（Fusarium solani f.sp. glycines，Fsg）引起。在一个埃塞克斯（Essex）×福里斯特（Forrest）重组自交系（RIL）群体中发现了6个数量性状位点（QTL），每个位点都赋予对SDS的部分抗性，但其作用模式尚不清楚。本研究旨在鉴定在接种Fsg后大豆根中mRNA转录本丰度发生变化的基因（EST）。用Fsg接种大豆品种福里斯特（有4个抗性等位基因）的根，14天后，相对于未接种根，利用抑制性消减杂交和差异显示技术富集差异表达的RNA序列。通过宏阵列杂交对这些RNA在接种和未接种根中的丰度进行定量。鉴定出一个由135个EST组成的单基因集，并用于进一步的宏阵列分析。与RIL 23（有6个抗性等位基因）未接种根相比，接种根中28个cDNA片段的丰度增加了两倍以上。在福里斯特和埃塞克斯（有2个抗性等位基因）中，与未接种根相比，接种根中只有一种mRNA的水平增加了两倍。在埃塞克斯，大多数分析的mRNA丰度下降（135个中有61个显示下降两倍），而在福里斯特，大多数mRNA丰度没有变化。在RIL 23中mRNA丰度增加两倍或更高的28个cDNA中，14%编码已知参与植物防御的蛋白质，21%参与代谢，14%参与细胞结构，4%参与运输。未注释的EST占基因的43%，4%的序列以前未知。对Fsg接种表现出差异反应的植物防御相关基因表明苯丙烷类途径在大豆对Fsg的防御中起作用。在埃塞克斯，参与植物防御、细胞壁合成、乙烯合成和代谢的基因在接种根中的表达水平较低。2基因、4基因和6基因聚合体之间的反应差异表明，SDS抗性QTL通过在接种/感染后维持或增加特定基因的表达来延迟症状或赋予抗性。
