Transcriptomic and Genetic Analysis of Seed Germination Vigor under Low Temperature in Weedy Rice WR04-6

Low temperature is one of the major factors affecting rice germination, and low tempera-ture germination (LTG) is an important agronomic trait. Although genetic variation is abundant in rice germplasm resources, the molecular mechanism of LTG remains poorly understood. In this study, we first proved that weedy rice WR04-6 had significantly better low-temperature germination (LTG) ability at 10°C than the cultivated rice Qishanzhan (QSZ). RNA-seq was used to investigate the gene expression of WR04-6 and QSZ at 10, 12 and 14 days of seed germination at 10°C. The results of GO enrichment and KEGG en-richment revealed that the differentially expressed genes between WR04-6 and QSZ were mainly concentrated on the response to starch catabolic processes and the response to ab-scisic acid. This is consistent with the results of a-amylase activity, ABA and GA treat-ment. A recombinant inbred line (RIL) population derived from a cross between WR04-6 and QSZ and its high density SNP genetic map were used to detect quantitative trait loci (QTL) for low temperature germination rates at 10°C for 14 days. The results showed that two new QTLs were located on chromosome 3 and chromosome 12. Combined with the mapped QTLs and RNA-seq differential genes (DEGs), sixteen candidate genes potentially associated with LTG were identified. Validation of expression of the candidates by qRT-PCR were consistent with the RNA-seq data. These results will enable us to under-stand the genetic basis of LTG in weedy rice and provide new genetic resources for gener-ation of rice germplasm with LTG. Overall design: An RNA-seq analysis was performed to further investigate difference between WR04-6 and QSZ. Low temperature (10°C) germinating seed of WR04-6 and QSZ were collected at 10, 12 and 14 days after imbibition, with three biological replications.