Proteomic and phosphoproteomic determination of ABA's effects on grain-filling of Oryza sativa L. inferior spikelets

Cultivars of rice (Oryza sativa L.), especially the large-spikelet-type, often fail to achieve the high yield potential due to poor grain-filling of their inferior (late-flowering) spikelets. The superior (early-flowering) spikelets normally contain more abscisic acid (ABA) than the inferior spikelets. It was speculated that ABA might play a pivotal role in the grain-filling of inferior spikelets. To understand the molecular regulation involved in this process, we employed the 2-D gel-based comparative proteomic and phosphoproteomic analyses to search for differentially expressed proteins in the inferior spikelets under exogenous ABA treatment. A total of 111 significantly differential proteins and 31 phosphoproteins were found in the inferior spikelets after treatment. Among them, 100 proteins and 23 phosphoproteins were identified by using MALDI-TOF/TOF MS. In addition, the gene expression patterns of the inferior spikelets were confirmed with RT-PCR. These differentially expressed proteins are active in defense response, carbohydrate, protein, amino acid, energy and secondary metabolisms, as well as cell development and photosynthesis. The results suggest that the grain-filling of rice inferior spikelets is regulated by ABA through some proteins and phosphoproteins participating in carbon, nitrogen and energy metabolisms.

► Proteomic and phosphoproteomic assay were conducted on the inferior spikelets of rice with the 20 × 10−6 M ABA and control treatments.
► A total of 111 proteins and 31 phosphoproteins were found to differ significantly with the exotgroen ABA treatment.
► The gene expression patterns of the proteins were confirmed with RT-PCR.
► ABA-response proteins and phosphoproteins are likely involved in the grain filling of inferior spikelets.