Comparative proteome analysis reveals the role of negative floral regulators and defense-related genes in phytoplasma infected sesame.

"Candidatus Phytoplasma australiense" is associated with floral malformations in sesame but the interaction remains largely unexplored. A label-free quantitative shotgun proteomics approach through liquid chromatography-mass spectrometry quadruple time-of-flight was used to analyze changes in the proteome of asymptomatic (control) and symptomatic (phytoplasma-infected) sesame plants to identify proteins differentially expressed during phytoplasma infection at early stages of flower development. A total of 3457 and 1704 proteins were identified from asymptomatic and symptomatic samples respectively through proteome profiling with three runs per sample. Several differentially abundant proteins (DAPs) were identified which might be involved in sesame-phytoplasma interaction. The DAPs identified were related to transcription, cell division, chromosome partitioning, defense mechanisms, negative regulation of flower development, amino acid transport and metabolism, signal transduction and RNA processing, and its modifications. Of these proteins, 21 were downregulated while 212 were significantly upregulated in symptomatic sesame plants compared to the control plants. The floral development-related proteins like UBP16 and DCAF1 were found to be downregulated while negative regulators/repressors of floral development genes, HUA2, PIE1, and ICU2, were upregulated in symptomatic samples indicating phytoplasma's role in altering the expression of these genes. Validation of these genes through quantitative retro-transcripted PCR suggested that the DAPs observed in symptomatic sesame might be induced by phytoplasma presence to suppress flowering via negative regulation of flower development.