Abstract
Vegetative-reproductive phase change is an indispensable event which guarantees several aspects of successful meristem behaviour and organ development. Antirrhinum majus undergoes drastic changes of shoot architecture during the phase change, including phyllotactic change and leaf type alteration from opposite decussate to spiral. However, the regulation mechanism in both of phyllotactic morphology changes is still unclear. Here, the Solexa/Illumina RNA-seq high-throughput sequencing was used to evaluate the global changes of transcriptome levels among four node regions during phyllotactic development. More than 86,315,782 high quality reads were sequenced and assembled into 58,509 unigenes. These differentially expressed genes (DEGs) were classified into 118 pathways described in the KEGG database. Based on the heat-map analysis, a large number of DEGs were overwhelmingly distributed in the hormone signal pathway as well as the carbohydrate biosynthesis and metabolism. The quantitative real time (qRT)-PCR results indicated that most of DEGs were highly up-regulated in the swapping regions of phyllotactic morphology. Moreover, transcriptions factors (TFs) with high transcripts were also identified, controlling the phyllotactic morphology by the regulation of hormone and sugar-metabolism signal pathways. A number of DEGs did not align with any databases and might be novel genes involved in the phyllotactic development. These genes will serve as an invaluable genetic resource for understanding the molecular mechanism of the phyllotactic development.
Highlights
The life cycle of higher plants develops sequentially through several distinct developmental stages: embryogenetic, vegetative, and reproductive stages
In the S4 position, all growth cones developed into spiral leaf primordial (Fig 1C). 75.6% and 84% of spiral leaf primordia were respectively measured in S2 and S3 (Fig 1D)
This study investigated the transcriptome profiles of vegetative-reproductive transition of Antirrhinum using Illumina RNA-seq and differentially expressed genes (DEGs) deep-sequencing technologies
Summary
The life cycle of higher plants develops sequentially through several distinct developmental stages: embryogenetic, vegetative, and reproductive stages. The mechanism underlying the vegetative-reproductive transition remain largely unknown, several studies using heterochronic mutants have revealed that the regulation of stem cell differentiation located on SAM plays a significant role in the phase change. The activity and growth of SAM determine overall plant architecture, dynamically controlled by complex and overlapping signaling networks, including the CLAVATA (CLV)-WUSCHEL (WUS) negative feedback loop, KNOX pathways, and in part through their effects on hormone signaling [6,7,8]. In parallel to the local activity of the WUS-CLV feedback system, the Class I KNOTTED1-like homeobox (KNOXI) gene is required throughout SAM to inhibit cell differentiation. KNOXI is closely connected with plant hormone signaling It promotes cytokinin accumulation by transcriptional activation of the cytokinin biosynthesis, which in turn activates KNOX genes, forming an apparent positive feedback loop [15,16,17]. High concentrations of auxin within SAM are associated with regions of leaf initiation, whereas the feedback between auxin and PIN-formed (PIN1) leads to the formation of local auxin concentration maxima [20,21,22,23,24,25]
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