Cloning,Functional Analysis And Application Of A Major QTL Conferring Resistance To Maize Rough Dwarf Disease

Maize rough dwarf disease(MRDD)is a viral disease of global,importance in maize production,especially in the Yellow and Huai River valleys,a major maize-producing area in China.Thus far,no resistance genes have been cloned.In our research,we focus on the identification,application,characterization of qMrdd1,and search for new locus related to MRDD resistance,all data were listed as follows:1.Based on Tao's work,we used fine-mapping populations derived from NT409 and NT411,HuangC and X178,finally mapped qMrdd1 into 125,214 bp and 253,484-bp region on chromosome 8,respectively.Altogether,qMrdd1 could be finally restricted into the 103,834 bp region flanked by markers S18 and K7-1.Genetic analysis showed that qMrdd1 can reduce disease severity index(DSI)by 7.95-32.50 and 16.24-34.00,separately.2.Together with positive 1145 BAC(resistance to MRDD),positive Huangzao4 BAC(susceptible to MRDD)and B73(susceptible to MRDD)reference genome,only one non-transposon-related genes,GRMZM2G435373,were predicted in the 103,834 bp region,named ZmGD1.Among the same inbred lines,there are two transscripts,and the long transscript has one more exon(the forth exon).In protein sequence homology analysis,the short transscript has high homology with others,while the long transcript with an additional fourth exon were only found in our research.A 2,548 bp helitron transposable element was found to insert in ZmGDI in the resistant 1145 rather than the susceptible Huangzao4 and B73,induces alternative splicing which results in a modified ZmGDI with an alternative exon 10.Over-expression transgenic analyze showed that ZmGDI is responsible for MRDD resistance.3.Gene expression levels are comparable between wild and resistance ZmGDI alleles and also did not change much after rice black stripe disease virus(RBSDV)infected,regardless the fact that the quantity of RBSDV mounted up rapidly in the susceptible maize 16 days after viral infection.,RT-PCR analysis between short and long transcripts validated this results.We predict that maybe the short transcript acts as functional one,instead of the long one.Subcellular localization showed ZmGDI is diffused in plant cytoplasm and membrane.4.Historical observation results declared that the decreased cell elongation is a major factor to shorten internode length.Aberrant vascular cylinders were found in the transection of ninth intemode and leaves in diseased maize,caused by a large increase in phloem cells.Yeast 2 hybrid showed ZmGDI don't directly interact with 13 RBSDV proteins.5.36 inbred lines with helitron transposon were screened from 956 inbred lines mainly distributed worldwide.We found 36 helitron transposons have no any sequence divergence.The insertion of helitron transposon is significantly related to MRDD resistance in 186 maize inbred lines.F2 population derived from P138 and JH59,P138 and Qi319,X178 and Dan3130,were evaluated on genotypes and phenotypes.Resistance of individual with helitron transposon insert were distinguished from those without helitron transposon insertion.All those results indicated that helitron transposon insertion is tightly related to MRDD resistance.6.Linkage analysis of RILs derived from HuangC and X178,80044 and 80007,GWAS analysis of 186 inbred lines showed two new loci,qMrdd2 on chromosomes 2 and qMrdd3 on chromosomes5,related to MRDD resistance.