The Fine Mapping And Regulation Model Research Of Common Wild Rice In Guangxi QTL QCTS12,A Locus Positively Responses Chill In Rice Seedling Stage

Rice(Oryza sativa L.)is a thermophilic crop that is highly susceptible to low temperature stress.The common wild rice in Guangxi Province(Oryza rufipogon Griff.)has the ability to tolerate chilling stress.It is great significance to understand the genetic and molecular mechanisms that underlying the chilling tolerance of common wild rice in Guangxi.In this study,DC90,a chilling tolerant chromosome segment substitution line(CSSL)generated by the introgression of DP 15(Guangxi common wild rice)in to recurrent parent 9311,was used to fine map a locus associated with chilling tolerance on the chromosome 12 of rice.The locus was narrowed down to 1.36-Mb interval.We tentatively designated it qCTS12.To dissect the mechanism underlying the chilling stress tolerance of qCTS12,comparative transcriptomic and proteomic analysis were performed to detect the differential responses of down-stream regulated genes and proteins that were induced by chilling stress treatment.Comparative transcriptome analysis revealed that 2348 differentially expressed genes(DEGs)were identified to involve in chilling stress response in DC90 and 9311.Among which,659 DEGs were exclusively identified in DC90 in response to early chilling stress,the majority of the DEGs were enriched in chloroplasts.This indicates that chloroplasts play an important role in rice response to chilling stress.Comparative analysis identified 206 and 155 DEPs in 9311 and DC90,respectively,in response to the whole period of chilling and recovery.The majority of them were located in the chloroplast,some of them belong to the 'ribosome','protein-chromophore linkage' and'14-3-3' components,and the other part participates in 'photosynthesis and light capture'processes.Short Time-series Expression Miner(STEM)analysis revealed distinct dynamic responses of chloroplast protein and its ribosomal protein between 9311 and DC90 in the chilling and recovery stage.The DC90 chloroplast protein and its ribosomal protein showed a'cold acclimation' process during the chilling stress stage.In the recovery stage,it showed a'de-acclimation' process.The difference was that the 9311 only had a 'cold acclimation'process but no 'de-acclimation' process.The analysis of stress physiology of both genotypes found that qCTS12 may maintained the constitutive activity of catalase(CAT).The steady CAT activity maintains the balance between hydrogen peroxide(H2O2)production and clearance in DC90 under chilling stress.In contrast,9311 significantly decreased CAT activity under chilling stress resulting in massive accumulation of H2O2 in vivo.The difference of CAT activity may be the reason that the chloroplast and its ribosomal proteins of DC90 and 9311 showed different stress response patterns in the chilling stress and the recovery.In summary,we have discovered a new rice chilling tolerance site qCTS12.qCTS12 mediates the balance of hydrogen peroxide scavenging and production under chilling stress to maintain the 'cold acclimation' and 'de-acclimation' processes of chloroplasts and its ribosomal proteins,and thereby improves the chilling tolerance of rice.