Gene Differential Expression And WOX Gene Family Analysis Of Dendrobium Catenatum Lindl. Treated With Different Plant Hormones

Dendrobium catenatum Lindl.is a perennial traditional Chinese medicinal herb of the orchid family with high medicinal,economic and ornamental value.Hormones play an important role in the growth and development of plants and the synthesis of active substances,and WUSCHEL-related homeobox(WOX)genes affects various developmental stages of plants by mediating the transduction of plant hormone signals,but there are few studies on the mechanism of D.catenatum responding to exogenous hormones.In this study,D.catenatum seedlings were treated with abscisic acid(ABA),auxin(IAA),jasmonic acid(JA)and salicylic acid(SA)to study the differential gene expression by transcriptome sequencing.And the response patterns of WOX gene family of D.catenatum were analyzed under different exogenous hormone treatments.The main results were as follows:1.The 6-month-old seedlings of D.catenatum sprayed with ABA,IAA,JA and SA at 3 and 6 h,respectively,were used for the transcriptome sequencing.Seedlings without any treatment were used as control check(CK).A total of 592,196,563 raw reads were obtained after transcriptome sequencing,and a total of 587,960,808 clean reads were obtained after removing adapter and low quality reads,with a Q30 mean of94.65%.A total of 20,280 unigenes were obtained after removing redundancy.Compared to the control,1,207,1,412,182,222,1,832,1,389,603,422 candidate differentially expressed genes(DEGs)were obtained after 3 h and 6 h of treatment with ABA,IAA,JA,and SA,respectively;and compared to 3 h of treatment,64,7,356,90 DEGs were obtained after 6 h of treatment with ABA,IAA,JA,and SA.2.GO,KEGG and COG functional enrichment analyses were performed on the12 groups of DEGs screened.Under ABA treatment,GO enrichment revealed that DEGs were significantly enriched in response to hormones and oxidoreductase activity;KEGG analysis showed that DEGs were enriched in cytochrome P450 pathway;in COG functional classification,DEGs had the most annotated results in signal transduction mechanism and secondary metabolite biosynthesis.Under IAA treatment,GO enrichment revealed that DEGs were significantly enriched in hormone-mediated signaling pathways and oxidoreductase activity;KEGG analysis showed that DEGs were enriched in plant hormone signaling pathways;in COG functional classification,DEGs had the most annotated results in secondary metabolites biosynthesis,transport and catabolism and signaling mechanisms.Under JA treatment,GO enrichment revealed that DEGs were significantly enriched in secondary metabolic processes,hormone biosynthesis processes,and response to hormones;KEGG analysis showed that DEGs were enriched in DNA replication and other secondary metabolite biosynthesis pathways;among COG functional classifications,DEGs had the most annotated results in metabolic and signaling mechanisms.Under SA treatment,GO enrichment revealed that DEGs were significantly enriched in oxidoreductase activity;KEGG analysis showed that DEGs were enriched in signal transduction and biosynthesis of other secondary metabolites pathways;among COG functional classifications,DEGs had the most annotated results in secondary metabolites biosynthesis,transport and catabolism and signaling mechanisms.The results suggest that all four hormones may be extensively involved in phytohormone signaling,antioxidant system and secondary metabolite synthesis and accumulation,among which JA and SA may also be related to biotic stress in plants.3.The members of 10 WOX gene family were identified in the D.catenatum genome,and the bioinformatics analysis showed that the WOX gene family members of D.catenatum were divided into WUS(WUSCHEL)clade(WOX2,WOX3 a,WOX3b,WOX4 and WOX5),intermediate clade(WOX9,WOX11 a and WOX11b)and ancient clade(WOX13a and WOX13b),and there were cis-acting elements associated with plant hormones in the promoter region of these members.To clarify Dca WOX genes functionality,we selected WOX2,WOX3 a,WOX5,WOX9,WOX11 b and WOX13 a from three clades for subsequent analysis.Subcellular localization analysis showed that all these members are localized in the nucleus,which suggested that they might function as transcription factors.Transient expression assay in Nicotiana benthamiana leaves showed that members of the WUS clade containing the WUS-box and EAR structural domains can activate expression of TOPLESS(TPL)gene,whereas members of the intermediate and ancient clades lacking these structural domains cannot activate the expression of TPL gene.Furthermore,the different expression patterns of the two copies of WOX3,WOX11 and WOX13 under different plant hormone treatments suggest that these genes possibly have undergo the differentiation during evolution.In this study,we analyzed the transcriptome data of D.catenatum treated with four exogenous hormones,annotated and clustered the gene functions of DEGs in different treatment groups,and found that these four hormones played important roles in the growth and development and the synthesis and accumulation of secondary metabolites in D.catenatum.Ten WOX gene family members were identified from the D.catenatum genome,their functions were analyzed and verified,and it was found that these members were involved in plant growth and development regulated by plant hormone signal transduction.There results laid a foundation for exploring the response of D.catenatum to exogenous hormones and the regulation of its growth and development by the WOX gene family,and provided a theoretical basis for the subsequent management and cultivation of D.catenatum.