Research On Late Blight Resistance And Amino Acid Transpoter Genes In Potato

Potato(Solanum tuberosum L.)belongs to Solanaceae family,which is the fourth most important crop after wheat,corn and rice,and becomes more and more popular because of its nutrient-rich and pollution-free.Therefore,the potato breeders pay more attention on its productivity and quality.1.The research on late blight resistance geness in potato.China is the largest potato producer in the world in the terms of cultivated area and total yield,but its unit yield is far behind the average.Late blight,caused by Phytophthora infestans,is one of most important responsible disease for the reduction of potato.Introgression disease resistance alleles from a wild potato,S.demissum,to cultivated potato is illustrated to be an effective and economical way to control potato late blight.Therefore,a key objective in our work was to dig out more disease-resistant genes from a Mexico wild potato species S.pinnatisectum.In this study,histology and RNA-seq analysis were conducted to illustrate the difference between susceptible cultivar S.cardophyllum and resistant wild species S.pinnatisectum after invasion of P.infestance,and to establish a LRR resistant gene library.The results are as follows:(1)In both resistant and susceptible potato leaves,P.infestans could complete its infection process until reproduction.And no structural difference and changes of P.infestans was observed between the two during the whole process.The pathogen could germinate,differentiate the appressoriun,infection vesicles,intercellular hyphae,haustorium,intracellular hyphae and generate sporangia on sporangiophores.(2)The disease development of late blight on S.pinnatisectum was delayed remarkably compared with the process on S.cardophyllum.Six hours post inoculation,the hyphae had expanded into the spongy tissue on S.cardophyllum,which took about 15.4% of the total examined infection point.Whereas,it was rarely to be observed in the spongy tissue on S.pinnatisectum at this time.The proportion of hyphae extended into spongy tissue was upto 50% on S.cardophyllum compared with 5.8% on S.pinnatisectum at 9 h post inoculation.After 12 h of inoculation,the pathogen had been expanded into palisade tissue,took about 24.8% on S.cardophyllum and 1.2% on S.pinnatisectum.After 3 days of inoculation,the remarkable lesions with fluffy hyphae and large number of sporangia were observed on S.cardophyllum,but not on S.pinnatisectum.(3)The histological differences were significant between S.pinnatisectum and S.cardophyllum.On S.pinnatisectum the epidermal cells connected to the infection point showed deeper staining of trypan blue at 6 h post inoculation;the mesophyll cells invaded by P.infestance showed obviously cell death at 12 h post inoculation;and necrosis zones emerged on the inoculation site at 3 d post inoculation.Contrastly,those phenomenons were not observed on S.cardophyllum,and the typical lesions of late blight were observed at 3 d post inoculation.(4)The RNA-seq analysis detected 126 differential expressed LRR-genes in S.pinnatisectum and S.cardophyllum challenged by P.infestance;92 genes were particularly expression in S.pinnatisectum;and 24 genes were induced expression in 9 and 12 hours post inoculation which may correlate with the mesophyll cell death.2.The research on amino acid transporter genes in potatoMoreover,a series of bioinformatics methods were used to predict amino acid transport vehicles(StAAT)related the quality of potato.The study the expression of some StAAT genes by qRT-PCR,and studied the effects of amino acid and protein uptake on the process of seeds and tubers' development,which provided theoretical basis for further study of the family members' function and utilization on potato protein accumulation and storage.The results are as follows:(1)A total of 72 potato amino acid transport genes(StAATs)were collected and predicted by three bioinformatics methods.They were divided into 12 subfamilies based on their phylogenetic relationship with Arabidopsis and rice and distributed on 12 chromosomes.These potato subfamily genes not only have similar introns,molecular weights,isoelectric point,amino acid length and conserved domains,but also similar with the same types of Arabidopsis and rice's genes structures.(2)Nearly one-third of StAAT genes(23 of 72)were derived from gene duplication.among which tandem duplication made the greatest contribution to the expansion of the StAAT family.The number of tandem replicates is about five times that of the segmental duplications,so the tandem duplication made the greatest contribution to the expansion of the StAAT family.And the expression patterns of these replication genes are different between each other.This may means that the replication phenomenon is important for the expansion of the AAT family members and the diversification of biological functions.(3)The gene expression profiles and qRT-PCR analysis showed that most of the StAAT genes have different expression patterns.Particularly,the StAAP and StAUX subfamily members may be involved in the transport and accumulation of amino acids in potato tubers.