Comparative de novo flower transcriptome analysis of polygamodioecious tree Garcinia indica

To extend our understanding of molecular mechanism of sex determination in agro-economically important, polygamodioecious tree Garcinia indica (Kokum), high-throughput, next-generation flower transcriptome sequencing (NGS), and comparative analyses were performed to investigate differentially expressed gene in bisexual, female, and male flowers. A total of 49414 unigenes in BS, 45944 unigenes in FL, and 49028 unigenes in ML flowers were annotated. KO annotations revealed that 25 functional categories were large number of genes which were annotated to 'signal transduction'. We identified 33 genes for 'auxin response factor' and 50 for 'ethylene-responsive factor' whose expression changed significantly in all the three paired library combinations. Furthermore, key regulators of floral development such as FLC, SVP, AP1, AP2, AP3, AG, AGL2, AGL4, AGL9, and PI were identified. A total of 327 differentially expressed MADS-box genes were identified in G. indica transcriptome. Analysis of MADS-box genes identified five genes such as MADS AGL11, CRS2-associated factor chloroplastic, conserved hypothetical protein, uncharacterized protein LOC104422218, and MADS-box JOINTLESS-like isoform X3 significantly expressed in only FL flower. In addition, number of DEGs like dynamin 2A, auxin response factor, and spermidine synthase involved in sex expression and reproduction were discovered. The expression patterns of selected genes matched well with the expression levels of unigenes by transcriptome sequencing. Our large-scale comparative analyses may provide valuable hints for the next insights into the molecular mechanism of sex determination in G. indica.