Proteomic analysis of rice embryo: An approach for investigating Gα protein‐regulated proteins

Abstract

The rice dwarf1 (d1) mutant, which lacks the alpha subunit of a heterotrimeric G protein (Galpha protein), shows abnormal morphology due to shortened internodes, dark green leaves and grains that are small and round. Proteome analysis was used in this study to aid in determining the function of Galpha protein in rice embryos. Using 2-DE, seven seed embryo proteins were shown to be down-regulated in the d1 mutant as compared with its wild type. These seven proteins included a receptor for activated C-kinase (RACK) and six rice embryo globulin-2 proteins (REG2). The six REG2 have similar molecular masses with minor differences in pI. In addition to the reduced accumulation of RACK in the d1 mutant, the increase in QL/d1, in which a constitutively active form of the Galpha protein is expressed, was significantly higher as compared with wild type. The level of accumulation of these seven proteins during seed development and maturation did not change significantly until the 2nd wk after pollination. Reduced accumulation of these seven proteins started in the d1 mutant at the 3rd wk after pollination, and continued until seed maturation was complete. All seven proteins were completely absent 24 h after imbibition in both d1 mutant and its wild type. However, the phytohormone abscisic acid promoted the expression level of RACK after imbibition in the wild type as compared with d1 mutant. These results suggest that RACK is regulated by Galpha-protein and plays an important role in a basic cellular process as well as in rice embryogenesis and germination.

Salt stress responses in Populus cathayana Rehder

“…The overexpression of WD-40 repeat proteins (spot 11) induced by abiotic stress has also been found in the proteomic analyses on rice seeds [57], young rice panicles under salt exposure [33] and germinating rice seeds upon copper exposure [58]. The WD-40 repeat protein family, including G protein, has been shown to play a role in numerous cellular functions, including signal transduction, mRNA processing, gene regulation, vesicular trafficking and the regulation of the cell cycle [59].…”

Study of novel d1 alleles, defective mutants of the .ALPHA. subunit of heterotrimeric G-protein in rice

“…Despite the simplified repertoire of Gα in plants, plant Gαs are concerned with signaling of many plant hormones (Chen et al, 2004;Pandey et al, 2006;Ullah et al, 2002), blue light (Warpeha et al, 2007), and D-glucose (Huang et al, 2006). In rice plants, the mutants of a Gα gene, d1s were originally identified in 1999 (Ashikari et al, 1999) and they have been used in subsequent G-protein studies (Komatsu et al, 2005;Ueguchi-Tanaka et al, 2000). d1s exhibit specific multiple abnormities in the gross phenotype (Fig.…”

RACK1 Functions in Rice Innate Immunity by Interacting with the Rac1 Immune Complex

“…RACK1A could also regulate the integrity of the Rac1 immune complex (indicated by light green) as a scaffolding protein. Heterotrimeric G proteins regulate expression of Rac1 (Suharsono et al, 2002) and RACK1 (Komatsu et al, 2005); thus, they influence rice innate immunity through their effects on these two molecules. principle focus.…”

“…A recent proteomic study of the rice dwarf1 mutant lacking the Ga subunit of heterotrimeric G protein indicates that, in the embryo at least, RWD (RACK1A) protein levels are reduced compared with the wild type (Komatsu et al, 2005). Heterotrimeric G proteins regulate innate immunity through Rac1 (Suharsono et al, 2002) and hormone signaling (Fujisawa et al, 2001) in rice.…”