The Response Of Hydroxyproline-rich Glyproteins In Banana To Low-temperature Stress And Its Characteristics Analysis

Banana(Musa spp.)is the most important tropical and subtropical fruit in China.Banana production in our country is often sufferred from chilling injury.Plant cell walls are the first line of defense when encountered stresses.Many studies have shown that hydroxyproline-rich glycoproteins(HRGPs),as structural proteins of plant cell walls,play an important role in plant stress resistance mechanisms.However,there are few studies involved in the relationship between the plant resistant to low temperature and important members of HRGPs,including arabidoglactan-proteins(AGPs),glycine-rich proteins(GRPs),lectin and proline-rich proteins(PRPs).In the present study,chilling-sensitive cultivar ’Baxijiao’(Musa spp.AAA)was used as plant material.The quantitative TMT(Tandem Mass Tags)technology was used to study the response of its proteins to low temperature.The chilling-responeded HRGP proteins and genes were selected for further study from these proteomics data and digital gene expression(DGE)data obtained.Then,chilling-sensitive cultivar ’Baxijiao’ and chilling-tolerant cultivar ’Dongguandajiao’(Musa spp.ABB)were used as plant materials to dectect the different changes in spatio-temporal expression of MaFLA11 between these two cultivars by immunofluorescene labelling techniques and to investigate the different expression of the above-selected HRGPs by qPCR technology upon both of artificial and natural low temperature stresses.Some of HRGPs genes were cloned from ’Baxijiao’ and ’Dongguandajiao’ respectively,and the different characteristics of these genes between these two cultivars were compared and analyzed.And HRGP genes members possibly,involved in chilling tolerance were discussed.The results can not only enrich the cold resistance mechanism of bananas,but also provide the target genes for banana cold resistance breeding.The main research results obtained are as follows:1.Responses of HRGP genes to low temperature stress at the transcript level: There were two AGP genes,five lectin genes and one GRP gene differently expressed under the low temperature stress in ’Baxijiao’ leaves.2.Analysis of proteomics data: TMT quantitative analysis of proteins identified a total of 110,693 spectra with definite identification information,identified 5744 proteins,and the spectral identification rate was 26%.Using 1.3 times as the difference threshold,366 differentially expressed proteins were obtained,of which 170 were up-regulated and 196 were down-regulated.Metabolic process was the most important biological processes item associated with the identified proteins.It was catalytic activity and cytoplasm and organelles for molecule function and cellular component items,respectively.In the KEGG database,the most annotated pathway is the metabolic pathway,followed by the biosynthesis and carbon metabolism pathways of secondary metabolites.3.Responses of the HRGPs to low temperature stress at protein level: There were two AGP proteins,one lectin protein,and one GRP protein in the ’Baxijiao’ leaf differently expressed.4.Differential expression of HRGPs in ’Baxijiao’and ’Dongguandajiao’: The differences in the expression levels of 11 HRGP members selected from the transcriptomics and proteomics data under artificial and natural low temperature stresses were investigated.The results showed that the expression levels of seven HRGP genes(MaFLA2,MaFLA8,MaLecRK-A4.2,MaLECRK-A4.3,MaLecRLK1,MaGRP7)were significantly higher in the chilling-tolerant cultivar ’Dongguandajiao’ than in the chilling-sensitive cultivar ’Baxijiao’ under lower temperatures,indicating that they may be related to the chilling tolerance of banana.5.Four HRGP genes,namely MaFLA2,MaFLA8,MaGRP1,and MaLecRLK1,were cloned from ’Baxijiao’ and ’Dongguandajiao’ respectively.Differences in.amino acid sequence were observed between these two ciltivars in all the four cloned genes except MaGRP1.