Effects Of High Temperature On Potato Growth,Tuberization And Dormancy And Mechanism Of Heat Stress Response

Potato(Solanum tuberosum L.)is annual plant which originated from South America.The optimum growth temperature for potato is 20-25?,while the best temperature for tuberization is 15-20?.Heat stress would cause excessive growth of plants and limited the yield and quality of tubers,even terminated the tuber dormancy.In this study,greenhouse experiments were performed to reveal the responses to heat stress(35°C during the day,28°C at night)of potato cultivars with different maturity.The RNA-seq technology was used to illuminate the differences of gene expression levels between heat-stressed tuber and the non-stress tuber.Furthermore,the hybrid of full-length transcriptome sequencing and RNA-seq was carried out to understand the mechanism of heat stress response of potato cultivars varied in thermotolerance.The main results are as follows:1.Fifty potato cultivars were cultured under normal temperature(18/22?,CK)and high temperature(28/35?,HS)to investigate the SPAD,plant height,tuber number per plant and the largest tuber weight per plant.Heat stress promoted plant growth,while inhibited tuber formation and swelling.High temperature could lead to heat sprouting,but cultivars varied in tolerance.Heat sprouted tubers returned to dormancy after harvest.The heat-stressed tubers of most cultivars had shorter dormant period than their non-stress tubers.2.The eyes of heat-stressed tubers(cv.Russet Burbank)and normal tubers were used as materials for RNA-seq.A total of 1201 genes showed significantly differential expression levels between HS and CK samples.The results of transcriptome analysis of this study were compared with transcriptome analysis of sprouted tubers with normal growth conditions,the results indicated some DETs were shared in both transcriptomes.The DETs were significantly enriched in GO terms such as protein processing,response to stresses,response to reactive oxygen species,nuclear and membrane.These results indicated that the gene expression level of normal germinated tubers was similar to that of heat sprouting tubers.3.The results of full-length transcriptome sequencing of heat-stressed and nonstress plants(cv.Atlantic and Chieftain)showed that different cultivars had both commonness and specificity in response to heat stress at gene expression level.A large number of DETs related to protein folding,stress response,active oxygen metabolism,catalytic activity,substance metabolism and organelles were found in both cultivars.This indicated that the heat response mechanisms of different cultivars were similar.The number of DETs enriched by the above terms in different cultivars varied greatly,Atlantic had more DETs when response to heat stress,and the differences were found in enrichment levels of GO and KEGG in specific terms between different cultivars,this suggested that Atlantic was more sensitive to heat stress in the level of gene expression than Chieftain,and the potato cultivars varied in thermotolerance had varied gene expression response to heat stress.4.There were 186 and 170 differentially expressed lnc RNAs(DELRs)identified in the leaves of Atlantic and Chieftain,respectively,between heat-stressed and nonstress plants.These results suggested that heat stress may cause changes in the expression levels of some lnc RNAs in potato leaves,and that most of them were upregulated(79% and 93%,respectively).5.There were 43 and 17 DETs encoding replication protein A(RPA)70 k Da DNAbinding subunit B/D in Atlantic and Chieftain,respectively.On the other hand,there were 94 and 9 lnc RNA-m RNA interactions related to RPA in two cultivars,suggesting that the expression level of RPA may affect the thermotolerance of cultivars.6.A total of 15 PEBP genes were identified by whole genome level analysis of the DM v6.1 annotation of potato and were named St PEBP1 to St PEBP15 according to their chromosome locations.These genes can be divided into FT,TFL,MFT and PEBPlike subfamilies.Under heat stress,St PEBP14 and St PEBP15 in leaves were downregulated whereas St PEBP10 in roots was up-regulated,suggesting that St PEBP14,St PEBP15 and St PEBP10 may play important roles in the response to heat stress of leaves and roots,respectively.