Subunit 6A was identified in this study in response to GR24 treatment. We speculate that it might play a role in the ubiquitinmediated protein degradation machinery in the SL signaling AG-013736 pathway. It remains to be determined whether this 26S proteasome regulatory subunit interacts with the D3-D14-D53 complex, and if it plays a role in the ubiquitin-mediated protein degradation machinery in the SL signaling pathway. In summary, the 8 differentially expressed proteins responded to SLs did not overlap with the 8 proteins that exhibited phosphorylation status changes. Thus, different approaches have apparent different sensitivities and specificities in the identification of proteins in response to SL treatment. An integrative approach to combine the use of multiple techniques may complement with each other and lead to better identification of molecular changes in rice plants. It will be of interest to determine the exact functions of the SL-regulated proteins identified in this work. Due to the inherent bias of the 2-DE approach toward the identification of more abundant proteins, components of signaling pathways with lower abundance would be more difficult to detect. Enrichment of these low abundant proteins using pre-fractionation methods and application of more sensitive technologies will be helpful. Cellulose is the most abundant biopolymer on earth and is found in prokaryotes, animals and plants. Cellulose fibrils provide essential strength to cell walls of land plants and algae within an integrated network of other polysaccharides, structural proteins, and sometimes lignin. Cellulose typically represents between 15– 45% of the cell wall biomass. The high strength of cellulose fibrils reflects the co-crystallization of numerous high molecular weight b-1,4-glucopyranose chains that are synthesized in close proximity. Cellulose within plant biomass is used as a renewable source of materials and, more recently, as a reservoir of glucose for biofuels or platform chemicals. The fine structure of cellulose fibrils is important for both types of uses. For example, the degree of cellulose crystallinity impacts the strength of plant fibers as well as the efficiency of enzymatic hydrolysis of cellulose. More avenues to generate plants with optimized cellulose properties will become available through a detailed understanding of how the biophysical features of cellulose are controlled by the biosynthetic process, a goal that has been challenging to achieve. The cellulose biosynthetic process is one of the marvels of nature. Activated soluble sugar in the cytoplasm is converted into the para-crystalline fibrils over a distance of a few nanometers by a plasma membrane-embedded protein nanomachine, the cellulose synthesis complex. CSCs contain multiple cellulose synthase catalytic subunits or CESAs. The recently determined crystal structure of a bacterial cellulosesynthesizing protein shows that a single protein synthesizes and translocates one glucan chain through the plasma WZ8040 membrane. Substantial structural similarities between bacterial and plant cellulose synthases support a similar mode of operation for plant CESAs. A key factor for the formation of the native cellulose I allomorph, in contrast to the antiparallel chain orientation in artificially regenerated type II cellulose, is the synthesis from the same end of many glucan chains in close proximity.