Characteristics Of Plant Growth And Transcriptomic Analysis Of Internode Elongation Mutant Ein1 In Fagopyrum Tataricum

The plant height of Fagopyrum tararicum is determined by the length of nodes and the number of stem nodes,which is an important factor affecting plant type.Crop plant type is an important agronomic character that determines crop yield.The improvement of plant type has played a crucial role in the breakthrough of crop yield.The yield of Fagopyrum tararicum urgently needs to be increased,but the studies on plant type improvement and ideal plant type are insufficient.Therefore,it is of great significance to study the physiological and molecular regulation mechanism of Fagopyrum tararicum plant type in order to analyze the growth and development laws of Fagopyrum tararicum and guide breeding for high yield.In this study,the mutant ein1 obtained by ⁶⁰Co-γradiation mutagenesis was used as the material,and wild-type Jinqiaomai2（WT）was used as the control.Phenotypic identification,observation of cell structured characteristics,investigation of agronomic and yield traits,exogenous hormone response,endogenous hormone detection,transcriptome analysis and other studies were carried out.The main results were as follows:（1）Phenotype observation showed that the mutant of Fagopyrum tararicum ein1 grew rapidly,internode elongation and plant height increased significantly at seedling stage,but the number of stem segments decreased and plant height decreased significantly to maturity.The phenotype was stable.In addition,the leaf angle of ein1 mutant was significantly smaller than that of WT,and the plant type was compact and the canopy was more reasonable,showing the potential for dense planting tolerance.（2）Cell structured observation showed that the stem cells of Fagopyrum tararicum ein1 mutant were significantly larger than that of WT,and the length and width of the stem cells was significantly increased,indicating that the internode elongation of Fagopyrum tararicum ein1 mutant was closely related to cell enlargement.（3）Field experiments showed that the plant height of ein1 was significantly higher than that of WT at the early growth stage,but the number of nodes increased slowly after grouting,and the plant height and branch numbers decreased significantly to maturity stage.The 1000-grain weight and yield of ein1 was significantly higher than that of WT,and the yield was as high as 3.4 t/hm²,34.62%higher than that of WT.The results showed that Fagopyrum tararicum ein1 had excellent characters such as lower plant height,better grain fullness and increased yield.（4）Exogenous hormone treatment showed that the internode length of ein1 was elongated by induction into GA₃and shortened by inhibition of PP₃₃₃,Indicated that ein1 was a GA-sensitive mutant.The plant height of ein1 was significantly higher than that of WT under GA₃and PP₃₃₃treatment.The plant height of ein1 treated with PP₃₃₃was the same as that of WT sprayed with H₂O,and the plant height of ein1 treated with H₂O was the same as that of WT sprayed with GA₃,while the WT leaf angle treated with GA₃became smaller.It is speculated that the internode elongation of ein1 and its leaf angle may be regulated by GA.（5）A total of 16 GA-like substances were identified by LC-MS/MS,among which 4 GA-like hormones were significantly different between ein1 and WT.The contents of GA₃₄,GA₄and GA₃in ein1 were 6.91,2.85and 1.18 times of those in WT,respectively,while the contents of GA₂₀were 0.33 times of those in WT.Among them,GA₄and GA₃have obvious biological activity.So they are considered to be the main GA-like hormones regulating ein1 internode elongation.（6）Transcriptome analysis of ein1 stems revealed 560 DEGs between ein1 and WT,including 41 transcription factors,3 GA synthesis and catabolism,15 GA signaling,and 25 DEGs directly related to stem development and growth.The expression of GA20ox1 was only 0.05times of that of WT,and GA2ox was 7.58 times of that of WT.QRT-PCR confirmed that GA20ox1 expression of ein1 was very low,while GA2ox expression was significantly increased,indicating that GA synthesis was inhibited and GA decomposition was enhanced in ein1 stem at flowering stage.In addition,q RT-PCR analysis found that the expression patterns of the 12 tested genes were consistent with the transcriptome sequence results,which confirmed that the transcriptome data was reliable.The expression levels of MYB32 and two WRKY28 transcription factors were increased in ein1,and GA signal transduction ATL6,PUB23,UNKL（Ft Pin G0003310400.01）and TIR1 were increased.WD repeat-containing protein 44,Ankyrin-2,RHA1B,UNKL（Ft Pin G0004799800.01）,RING-type zinc-finger,F-box,and WD-40 domains protein 1/11,SCF ubiquitin ligase complex,26S proteasome regulatory subunit N10,26S proteasome regulatory subunit 6B and 26S proteasome regulatory subunit T3 gene expression decreased,stem growth and development related genes CCR,CAD,CESA and cell wall related receptor kinases were up-regulated,down-regulated expression of XTH,PL and BGALs,among the 4 PE genes,3 were down-regulated and 1 was up-regulated,among the 8 cellulase-related genes,4 were down-regulated and 4 were up-regulated.Therefore,it is preliminarily speculated that the accumulation of active GA₄and GA₃in ein1 can induce the up-regulated expression of MYB32 and WKRY28,inhibit the expression of GA20ox1,lead to the decrease of GA₂₀content,enhance the expression of GA2ox,and promote the decomposition of GA₄into GA₃₄,and regulate the expression of 12 ubiquitination ligase genes and 3 26S protease genes in GA signal transduction.Furthermore,it regulates the expression of 25downstream genes related to stem growth and development,thereby jointly controls cell enlargement and stem elongation.In summary,we found that Fagopyrum tararicum ein1 was an excellent semi-dwarf bar high-yielding mutant with internode elongation,reduced node number,compact plant type and good grain fullness.Internode elongation was regulated by excessive accumulation of GA-like hormones.GA-like hormones may jointly determine the plant type of ein1 by controlling the expression of genes related to signal transduction and growth and development.However,the cause of GA excess accumulation in ein1 remains unclear,and whether GA excess accumulation affects signal transduction and stem growth-related gene expression needs further investigation.