This study was aimed at the identification and quantification of the
protein components of the pollen grains in parallel with the distal stigmatic tissue of
tetraploid cultivars.
Proteomes were analyzed using iTRAQ 4plex labeling,
peptides separation by online RP-nano-LC and analysis by ESI-MS/MS.
Protein identification and quantification were made using the Asparagales database as a reference. A total of 524,037 MS/MS spectra were produced from pollen and stigma samples. From these, a total of 8368
peptides wereidentified corresponding to 994 unique
peptides and 432
protein groups. Among them, 128 differentially expressed
proteins were retained for further analysis. In absence of the daylily genome availability, we exploited numerous databases and bioinformatics resources to exploring the putative
biological functions of these
proteins. The profile of differentially expressed
proteins suggests an important representation of functions associated to the signalling and response against endogenous and environmental stresses, including several
enzymes implicated in the biosynthesis of
antibiotics. The abundance in stigma of several structural
proteins of the ribosomal sub-units as well as of the core
histones suggest that the translation processes and the regulation of gene expression in stigma is a more active mechanism than in pollen. In addition, pollen prioritizes the synthesis of
fructose and
glucose as opposed to
sucrose in stigma as a source of energy. Finally, the modulated
proteins in Hemerocallis point to several pathways that give potential clues concerning the molecular mechanisms underlying the functions of the pollen and the stigmatic fluid in daylily reproduction.