Screening And Identified For Chilling Tolerance Tomato Under Radiation Mutagenesis And Transcriptome Analysis

Tomato is a chilling tolerance crop that is vulnerable to chilling injury.To screen for chilling tolerancetomato mutants,seeds were irradiated with different doses of ⁶⁰C0-?and then screening the individual plant of chilling tolerance generational.The M3-generationa chilling tolerance mutant was evaluated according to the physiological index of the relative electrical conductivity,the content of proline and alondialdehyde.The cold-resistance of No.467 plant was significantly higher than CK.The stoma features of chilling tolerance mutant No.467 tomato were observed and the resultsshowed that the cold-resistance of mutant is related with stoma density and stomatal aperture instesd of stomatal size.Furthermore,by quantitative analysis,the significant stomatal density change of chilling tolerance mutant No.467 is caused by the abnormal expression of stomatal development-related genes,such as SPCH?MUTE?FAMA.We found that after 24h low-temperature treatment,the chloroplasts of No.467-2 were close to the edge of the cell and the vacuole was clear and visible;however,the shape of the chloroplasts and grana showed no obvious changes.In contrast,the leaf vacuoles of the controlplants were invisible,and the cells were filled with fractured tissues;the chloroplasts were swollen,and the grana were hard to identify.Some chloroplasts even appeared damaged,cindition,and the granalstructure was disorganized.Submicroscopic structure observation of the chilling tolerance mutant No.467-2 showed the retention of intact membranes and organelles in good condition,which has greatsignificance in maintaining photosynthesis.The mutant tomato were further analysised by using high-throughput next generation sequencing.Between the comparison of CK unchilling and chilling varieties,1509 differentially expressed genes were identified,of which 1007 were upregulated and 502 were downregulated.From the comparison of M unchilling and chilling varieties,1398 differentially expressed genes were identified,of which 751were upregulated and 647 were downregulated.There are 726 different genes with significant changes between mutant and CK were screened and annotated.Analysis of uni-transcripts indicated that 9 gene ontology terms were enriched significantly in CK and 16 GO terms were enriched significantly in M.For further analysis of the variable genes by KEGG pathway,the flavonoids biosynthesis andphenylpropanoid biosynthesis two important materials biosynthesis pathways,significantly enriched in No.467 cold resistance mutants.This paper selected important up regulation genes from the metabolism and biosynthetic pathways.Lay the foundation for acquire cold resistance of transgenic tomato.