Proteomic Analysis Of Mature And Germinated Pollen Grains From Oryza Sativa L. Ssp Japonica

As a highly reduced two-/three-cell organism, the pollen performs specialized functions to generate and carry sperms into the ovule by its polar elongation. Pollen has been the well model to investigate the sexual reproduction and cell polar growth in the past years. Yet molecular genetic basis of these functions is devoid now.Our proteomic analysis of mature pollen grains from Oryza sativa L. ssp japonica by a combination of 2DE with MALDI-TOF MS and ESI-Q-TOF MS/MS revealed that total 322 unique proteins expressed in three distinct protein fractions(pollen coat proteins, pollen coat/wall related and releasing proteins and pollen interior proteins). These proteins involved in signal transduction (10%), wall remodeling and metabolism (11%) and protein metabolism (14%), along with carbohydrate and energy metabolism (25%), were over-represented in pollen protein complement, some of which were important proteins identified in pollen firstly, mainly involving in signal transduction (such as protein kinases, receptor kinase-interacting proteins, GDP dissociation inhibitors, C2 domain-containing proteins, cyclophilins), protein synthesis, assembly and degradation (such as prohibitin, mitochondrial processing peptidase, putative UFD1, AAA+ ATPaes), and wall remodeling and metabolism (such as reversibly glycosylated polypeptides, cellulose synthase-like OsCsLF7). And bioinformatic analysis revealed that about 11% of the identified proteins were functionally unknown and did not contain any conserved domain associated with known activities. Also, five novel proteins were identified by de novo sequencing. The biological functions of pollen-expressed proteins including functionally unknown proteins and novel proteins need to be investigated further.Furthermore, a proteomic comparison between germinated pollen grains and mature pollen grains from rice resulted in the identification of 160 differentially-expressed identities (represented 120 unique proteins) upon germination, which could be assigned into 13 function categories by bioinformatic analyses. Of them, over-reperasentative proteins were those involved in the wall remodeling and metabolism (24% of the identities, such as UDP-glucose pyrophosphorylase and calss III peroxidase), protein metabolism (11%, such as eIF4A, members of 20S proteasome subunit), cytoskeleton dynamics (8%,...