Abstract
The measurement of gene expression can provide important information about gene function and the molecular basis for developmental processes. We analyzed the transcriptomes at three different developmental stages of pepper flower [sporogenous cell division, stage (B1); pollen mother cell meiosis, stage (B2); and open flower (B3)]. In the cDNA libraries for B1, B2, and B3: 82718, 77061, and 91491 unigenes were assembled, respectively. A total of 34,445 unigene sequences and 128 pathways were annotated by KEGG pathway analysis. Several genes associated with nectar biosynthesis and nectary development were identified, and 8,955, 12,182, and 23,667 DEGs were identified in the B2 vs B1, B3 vs B1, and B3 vs. B2 comparisons. DEGs were involved in various metabolic processes, including flower development, nectar biosynthesis, and nectary development. According to the RNA-seq data, all 13 selected DEGs showed similar expression patterns after q-PCR analysis. Sucrose-phosphatase, galactinol-sucrose galactosyltransferase, and sucrose synthase played very important roles in nectar biosynthesis, and CRABS CLAW could potentially be involved in mediating nectary development. A significant number of simple sequence repeat and single nucleotide polymorphism markers were predicted in the Capsicum annuum sequences. The new results provide valuable genetic information about flower development in pepper.
Highlights
Most flowering plants attract pollinators by offering a reward of floral nectar in many plant-pollinator systems
Global gene expression patterns in pepper flowers High-throughput mRNA sequencing technology is highly suitable for gene expression profiling in non-model
Most pepper sequence studies were based on EST sequencing, very few tags had been reported in public databases, and there was little available genetic or genomic information
Summary
Most flowering plants attract pollinators by offering a reward of floral nectar in many plant-pollinator systems. A floral organ called the nectary is responsible for nectar biosynthesis. The molecular events associated with the biosynthesis of nectar and nectary development are not clearly understood. Only a few individual genes, including BLADE-ON-PETIOLE (BOP) 1, BOP2, and CRABS CLAW (CRC) have been isolated and confirmed to be associated with the development of the nectary (Lee et al, 2005a; McKim et al, 2008). Previous research has shown that crc knockout mutant lines failed to develop a nectary, whereas bop1/bop double mutant plants have significantly smaller nectaries along with aberrant morphologies (Bowman and Smyth, 1999; McKim et al, 2008). CRC expression is essential, it cannot promote ectopic nec-
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