Genome-wide Identification and Evolutionary Analysis of the SMXL Gene Family in Four Sapindaceae Species and Expression Analysis of DlSMXLs during Somatic Embryogenesis in Longan
[Objective]To provide a theoretical reference for the study of the biological characterization of the SMXL family of Sapindaceae,and to delve into the regulatory mechanism of this gene family in the abiotic stress response of Sapindaceae plants.[Method]Based on the amino acid sequences of the SMXL family of the model plant Arabidopsis thaliana,TBtools was used for genome-wide identification of SMXL family members from longan,rambutan,sapindus,and litchi.MEGA11 was used to construct the phylogenetic tree,and online software such as Expasy,WoLF PSORT,MEME,STRING,PlantCARE,etc.were used to predict the protein physicochemical properties,subcellular structural localization,conserved motifs,protein interactions,cis-acting elements,etc.respectively.Longan transcriptome data were also utilized for expression analysis in the early stages of somatic embryogenesis.[Result]Forty-eight SMXL family members were identified in four Sapindaceae species,including 11 in longan,11 in rambutan,9 in sapindus,and 17 in litchi.According to the classification of the SMXL family of Arabidopsis thaliana,the SMXL family members in four Sapindaceae species could be divided into 5 subfamilies,and the subcells were located in chloroplasts,nuclei,cytoplasm or mitochondria.Protein interaction analyses showed that SMXL family members in Sapindaceae could interact with a variety of proteins,which were mainly classified into two categories:one with the heat shock proteins(HSP)or CLP,which were abundantly expressed when subjected to abiotic stress;the other interacted with the strigolactone receptor protein D14,the karrikin receptor protein KAI2,and the MAX2 protein,which regulated the SL signaling pathway.The results of the cis-element analysis showed that among the SMXL family members of the four Sapindaceae species,there were more light-responsive elements,anaerobiosis-inducible elements(ARE),and abscisic acid-responsive elements(ABRE),etc.Therefore,it was hypothesized that the SMXL members were largely involved in the response to abiotic stress in Sapindaceae.Furthermore,there were five different expression profiles of the DlSMXL family during the early SE in longan,with the DlSMXL4 showing higher expression at embryogenic callus(EC),incomplete compact pro-embryogenic(ICpEC),and globular embryos(GE)stages compared with the other members.Based on analysis of transcriptomic data at longan EC treated with 5-azacytidine,PEG,SL,light,temperature,and various hormones,it could be seen that DlSMXL5 expression was significantly increased by drought,GR24,darkness,and high-temperature treatments.It is hypothesized that this member is capable of maintaining embryonic healing tissue morphology in response to phytohormones and stressful stresses.Secondly,DlSMXL8 was up-regulated after 5-azacytidine treatment,which might be involved in DNA methylation playing a role during somatic embryogenesis in longan.[Conclusion]As well as playing a critical role in plant growth and development,the SMXL family of four Sapindaceae species is also widely implicated in the regulation of abiotic stress.Our results provide a theoretical basis for the classification and biological function of SMXLs in the Sapotaceae and give a better understanding of the functional validation of SMXLs in early somatic embryogenesis longan.
SapindaceaeSMXLGenome-wide identificationEvolutionary analysisEarly somatic embryogenesis in longan
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