Study On Structural Characteristics And Endogenous Hormones Regulation Mechanism Of Chimonobambusa Utilis Keng F.

Different from the normal circular-stem plants,the Chimonobambusa utilis keng f.presents an unusual square-like culm.Such structural can improve transverse tensile strength and prevent the bamboo from expansion and slit.Furthermore,it also provides protections from the varied environmental load,such as prevailing wind,snow,and gravity,bringing about the beneficial effects of inheritance or development.It has a long history after being discovered and christened ‘square bamboo’.The macrostructure and microstructure were attracted by researchers but studied little in this aspect.Moreover,underling formation mechanism of square-like stems in physiological and molecular levels has not been investigated.Multi-omics analysis has been applied for revealing the physiological and molecular biological characteristics in plants during growth development.To investigate the biomolecular function and regulation mechanisms associated with square-like stems in our work,microscopic image analysis system,liquid chromatography tandem mass spectrometry,and RNA-seq technologies were applied for performing comprehensive analysis of macrostructure,microstructure,hormone concentrations,transcriptomics,and metabolomics.Therefore,plant hormones,differentially expressed genes(DEGs),and differentially accumulated metabolites(DAMs)were detected,then a transcriptional and metabolic regulatory network has been established based on plant hormone synthesis and signal transduction.The main results are as follows:(1)Macro characteristics indicate that the geometric form of the cross-sections of stems are approximately as a square-like because of the difference of stem wall thickness(SWT)between the corner(CR)and side regions(SR).The results show that values of SWT were5.74 mm and 3.92 mm at CR and SR,respectively.It showes a trend of CR > SR,and radius of curvature also showes the same variation pattern.Besides that,the squircle form has been confirmed for fitting square-like stems data based on the hyperelliptic equation.(2)Micro characteristics indicate that the formation of square-like stems is closely related to the difference of fibres morphology between CR and SR.The results show that values of fibre wall thickness(FWT)of stems were 0.66 μm and 0.92 μm at CR and SR,respectively.It showes a trend of CR < SR,and fibre lumen diameter,radial and tangential diameters of vascular bundles also show the same variation pattern.Moreover,the difference of the anatomical characteristics mentioned above were all significant at 0.001 level,and the FWT was the highest.(3)Physiological characteristics indicate that the formation of square-like stems is closely related to the difference of Auxin,Jasmonate,and Cytokinin concentrations between CR and SR.The results show that a total of 88 plant endogenous hormones were detected from all comparison groups,38 of them at CR and SR are different with each other.Auxin compounds(IBA,IAA,IAA-Val-Me,TRA,TRP),Cytokinin compounds(BAP,i P9 G,DHZROG,c ZROG,t Z),Jasmonic acid compounds(OPC-4,JA-Val,JA-ILE,JA,MEJA,OPDA),and salicylic acid compound(SAG)showed a trend of SR > CR,the ratio of GA/AUX,CTK/AUX,and GA/ABA showed a trend of CR > SR.(4)Transcriptome and primary metabolome analyses indicate that the formation of squarelike stems is closely related to the phenylpropanoid biosynthesis and Linoleic acid metabolism pathway,and the differentialy expressed levels of Jasmonates biosynthesis and signal transduction-related genes between CR and SR.The results show that a total of 227.5Gb Clean Data was obtained from all comparison groups.A total of 514 DEGs were obtained,360 of them referred to up-regulation and 154 of them referred to down regulation.The counts of DEGs those were enriched in phenylpropanoid biosynthesis pathway are the most.A total of 82 metabolites were detected from all comparison groups.The counts of DAMs those were enriched in linoleic acid metabolism and α-Linoleic acid metabolism pathways are the most.It is found that a strong correlationship existed between the square-like stem and jasmonic acids biosynthesis and signal transduction-relate genes,according to combined analysis of transcriptomics and metabonomics.(5)A transcriptional and metabolic regulatory network has been obtained based on plant hormone synthesis and signal transduction.It is found that 105 DEGs have a strong correlation with N6-isopentenyladenosine(5),salicylic acid(13),cis-Zeatin riboside(11),Jasmonic acid(10),tryptamine(19),L-tryptophan(23),3-Indolebutyric acid(13),and Indole-3-acetic acid(11)from H30 CR＿vs＿SR comparison group.Among them,66 DEGs have a strong correlation with Auxin,followed by Jasmonates and others.Therefore,the results suggest that Auxin and Jasmonates may play a major role in the formation of squarelike stems.The following corn enzymes and genes may involve in the development regulation of square-like stems: PTAL,POD,E3 ubiquitin-protein ligase RHA2,AFU,UCHL36/42,and AUX/IAA related to Auxin biosynthesis and signal transduction,LDOX,ACC and MYC2 related to Jasmonates biosynthesis and signal transduction.