| As one of the most important economic bamboo species with the excellent ecological,economic and cultural value in China, moso bamboo is one of the highest growth rates in theworld. To study the molecular mechanism involved in its rapid proliferation and differentiationcharacteristics (shoot in winter or spring, young banboo after leaf expansion, abbreviatedshoot-culm), we performed transcriptome sequencing and mapped to the moso bamboogenomic resources (reference genome and genes) to produce a comprehensive dataset for thefast growing shoots of moso bamboo in order to pool the differentiation expressed genes basedon different kinds, and development stages. Moreover, the concentrations of endogenoushormones in different development stages and positions of bamboo were detected, andanatomical structures of shoot tips were also assayed. We further want to screen out genesrelated to signal transduction of auxin and perform cluster analysis, and then find the candidategenes, detect their dynamic expression profiles in different developmental stages, and clone theCDSs of them. The impotent results are listed as following,1. Transcriptome sequencing for moso bamboo was performed, and10,689genes with|log2Ratio (RPKM-H RPKM-CK)|≥2and FDR﹤0.001were characterized as the mostdifferentially expressed genes.6,076genes were up-regulated while4,613down-regulatedgenes which were classified into functional categories. Candidate genes which mainly involvedtranscript factors, plant hormones, cell cycle regulation, cell wall metabolism and cellmorphogenesis genes were further analyzed and the results showed that they may form anetwork that regulates the fast growth of moso bamboo shoots. Specifically, the differentialexpression candidates included1,154plant hormones related genes, more than11%of it, while169of them are auxin-related genes which presenting a larger weighting in whole planthormones. 2. The concentrations of five endogenous hormones, including indole acetic acid(IAA),gibberellic acid(GA3), zeatin riboside(ZR), brassinosteroid(BR) and abscisic acid(ABA)fluctuated overall showed increase-then-decrease profile during the development stages ofshoot-culm, among which IAA、ZR presented mono-peak curve, GA3presented double-peakcurve, and BR showed tri-peak curve, while ABA were significantly different and evenopposite, which was at the highest level in winter shoot, decreased significantly with thegrowth of shoot, and then showed a clear upward trend in the later. The relative concentrationfor these five hormones almost appeared mono-peak profile based on the developmental stagesand the peak season occurs at the height of1m or6m. Given the fact that the base of mosobamboo elongates mainly during the1m period and the middle extends mainly during the12m period. Moreover, there was a strong correlation between the concentration of hormoneswhich can induce cell elongation and cell division such as IAA、GA3、ZR and BR with theconcentration of ABA which inhibits the division of cells. It should be noted that the relativeconcentration of IAA was the highest at the top edge of bamboo, and showed reductionsignificantly and continued their downward trend, which was corresponding to large differencein auxin-related genes’ expression of transcriptome.3. Histological observations for tender tips of bamboo shoots indicated that meristem isstill showing strong cell division activity at least at6m height, their growth, differentiation andelongation was accompanied with the differentiation of main lateral bud, the growth,elongation and differentiation of secondary buds from lateral bud, and then down-differentiatedalong the stem and grow up to form the intact lateral bud system. The process is very impotentto the fast growth features. Besides, the thriving cell division and cell differentiation of bambooshoot tip lead to the small and tender phase of shoot and lateral bud. This development patternswas corresponding to the auxin concentration in this position at every development stage.4. According to the results of transcriptome for the moso bamboo, combined with ELISA,histology analysis, auxin and its related genes play important roles in the development ofbamboo shoot to bamboo. Three auxin-related gene including PheLAX3, PheARF and PheSAUR were further performed bioinformatic annotation, expression pattern and CDScloning.The cluster analysis of PheLAX3、PheARF、PheSAUR between moso bamboo andArabidopsis thaliana and rice reveled that these genes may be responsible for the cell division,cell differentiation and cell elongation. The gene expression based on qRT-PCR for revealedthe PheLAX3expression was positional specific, the top edge was the highest and reached thepeak at6m stage. PheARF expression was more stable at the edge of bamboo and was thehighest at9m stage. As for PheSAUR, its expression at proximal knob was stable; reached thehighest level when the heights from3m to12m, corresponding with the rapid growth of culmin the middle of bamboo. Moreover, the whole sequences of CDSs for PheLAX3, PheARF andPheSAUR were cloning successfully as PCR and sequencing shown, which make it possible toperform further genetically modified bamboo. |
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