Effects Of Polyploidy On The Delayed Senescence Of Rice Seeds And Its Regulation Mechanism

Seed of rice is an important strategic resource for ensuring the security of China’s staple food.Seed deterioration as a result of senescence is a major problem during seed storage,which can cause major economic losses.Screening among accessions in rice germplasm resources for traits such as slow senescence and increased seed longevity during storage is,therefore,of great significance.However,studies on delayed senescence in rice have been based mostly on diploid rice seed to date.Despite better tolerance for polyploid rice seed,the delayed senescence properties and delayed senescence related regulatory mechanisms of polyploid rice seed are rarely reported,due to the lack of polyploid rice materials with high seed set.In this paper,rice seed of A1,A2,A3,T1,Fengliangyou 4,9311-2x,9311-4x,bll-2x,bll-4x,Gaoshan 1 and Yang 6,were studied.After the artificial aging treatment in high temperature and high humidity environment,the difference in resistance to aging of different ploidy rice seeds was compared.It was found that the delayed senescence of the polyploid rice seeds was higher than that of the diploid rice seeds.Further analysis showed that the delayed senescence of the polyploid rice seeds was formed in the process of seed ripening,and reached the highest point when the rice seeds were riped.In the process of artificial aging,the RNA integrity of different ploidy rice seeds decreased,and that of diploid rice seeds decreased faster.Multiple comparisons of differential genes between 9311-4x and 9311-2x,A3 and 9311-2x,and A3 and 9311-4x showed that after tetraploid rice seeds were obtained from conventional diploid materials through chromosome doubling,the genes regulating heat shock protein were increased,and the genes regulating antioxidant activity were up-regulated,but the difference gradually became smaller at the 12 th day of artificial aging.Through small RNA high-throughput sequencing analysis and degradation sequencing analysis,40 known mi RNAs and 58 new mi RNAs were identified in rice seeds.According to the differential degradation fragments,1865 target genes regulated by mi RNA were identified,and 38 target genes were differentially expressed.After polyploidization,osa-mir164 d,which was significantly down regulated,was significantly enriched in the RNA degradation pathway,that is,the regulatory gene fragments involved in RNA degradation increased after polyploidization,the expression level of degradation related genes was low,and the RNA integrity was better.3816.0 proteins were identified by proteomics,of which 2983.0 were quantifiable.Based on the analysis of biological regulatory interaction network of differential genes,differential proteins and mi RNAs in different ploidy rice seeds,it was concluded that the down-regulation of osa-mir164 d led to the up-regulation of catalase activity regulatory genes and interaction genes(peroxidase regulatory genes,superoxide dismutase regulatory genes,etc.),and finally led to the differential expression of translation proteins.15 heat shock proteins with P < 0.01 were screened by proteome and transcriptome association analysis,and six corresponding genes were differentially expressed in the transcriptome.The results showed that limonene content in tetraploid rice seeds was higher than that in diploid rice seeds,so limonene was selected as a potential biomarker.Limonene can activate the defense system of antioxidant enzymes.We believe that limonene may be associated with antioxidant enzyme activity and can be used as a biomarker to rapidly evaluate thedelayed senescence of rice seeds with different ploidy by gas phase ion mobility spectrometry(GC-IMS).