Mechanism underlying root primordium development in Phoebe bournei cuttage
The main technique for asexually propagating of Phoebe bournei is through cutting;here,the mechanisms of root primordium development in P.bournei under original conditions were investigated using unprocessed cuttings without plant hormone treatment.At the initial stage of cutting(T0),early stage of root primordium appearance(T1),and differentiation stage of root primordium development(T2)of P.bournei cutting rooting,stem segments measuring 0.5～1.0 cm at the base of the cuttings were sampled for histological observations.Indole-3-acetic acid(IAA)content measurements and transcriptome sequencing were performed on the outer cortex of stem segments within 2 cm of the cutting top bud and base incision.Soluble sugar and soluble protein contents in the basal cortex were measured.Our results indicate that the root primordium of P.bournei cuttings originates from the thin-walled cells of the secondary cork cambium formed exterior to the vascular cambium.During P.bournei root primordium development,soluble sugar and soluble protein contents in the cortex continuously decreased in the T1 and T2 stages,whereas the cortex IAA content increased significantly(P<0.05),indicating that IAA is an important endogenous signal for root primordium development.The IAA content in the buds decreased during the T1 stage and then increased during the T2 stage,possibly indicating IAA transport from the buds to the cortex.On the basis of phylogenetic relationships,the 58 PbARF genes in the P.bournei genome can be classified into four clade:clade A,B,C,and D.During the development of P.bournei cutting roots,the expression levels of genes PbARF2,PbAR6,PbAR23,PbAR33,PbAR40,and PbARF58 gradually increased,indicating their significant roles in root primordium development.Moreover,PbAR33 and PbAR40 exhibited relatively high expression levels,suggesting that they are key genes involved in root primordium development.
Phoebe bourneicuttageroot primordiumindole-3-acetic acidARF gene family
国家科技期刊平台
NSTL
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