Transcriptome analysis reveals genes expression pattern of seed response to heat stress in Brassica napus L.

Seeds might deteriorate,and lose the ability to germinate when stored under high temperature and high humidity.Brassica napus is one of the most important oil crops in China.However,B.napus seeds were generally stored through summer season with high ambient temperature,which lead to seed viability loss.In order to understand the mechanism of seed response to heat stress and improve seed heat tolerance,B.napus seeds were treated with high temperature(40℃)and ultra-high temperature(60℃)for 4 h.The germination of heatstressed seeds were obviously slower,the germination index and vigor index decreased with temperature increase from 40 to 60℃,and the 40℃ pretreatment could improve the seed tolerance to 60℃ heat stress.Transcriptomics results showed that 442 differentially expressed genes(DEGs)were identified in seeds after heat stress.Gene ontology and KEGG pathway enrichment analysis revealed that some of the genes were involved in posttranslational modification,protein turnover,chaperones and carbohydrate transport,metabolic pathways and secondary metabolites biosynthesis pathway.Among these DEGs,sHSP and transcription factors genes were involved in heat stress tolerance.Thirty-two overlapping genes under different high temperature stress(40℃ and 60℃)were enriched in biological processes of response to oxidative stress and abiotic stimulus.The expression trends of 12 genes randomly selected from the RNA-seq data were almost consistent with the results of qRT-PCR.Our results revealed several potential candidate genes and pathways related to heat responsive by high temperature,which is beneficial for further improving the heat tolerance in B.napus seeds.

Identi cation of seed heat tolerance and its correlation with agronomic traits in Brassica napus L.

To better understand the effect of high temperature on seed viability, artificial aging treatments were implemented on 472 accessions of rapeseed (Brassica napus L.) by constant high temperature at 70℃for 8h. Results showed a remarkable impact of constant heat on seed germination. After heat treatment, considerable variation was found in seed germinability, some genotypes even lost the ability to germinate. The effect of accelerated aging was highly significant. Germination parameters varied among ecotypes. Seed viability varied with different origin, and was significantly and positively correlated with seed yield per plant and dry weight of aboveground parts per plant among 14 agronomic traits. Germination traits were positively correlated with oil contents.