The chloroplast protein BPG2 functions in brassinosteroid‐mediated post‐transcriptional accumulation of chloroplast rRNA

Abstract

SUMMARYBrassinazole (Brz) is a specific inhibitor of the biosynthesis of brassinosteroids (BRs), which regulate plant organ and chloroplast development. We identified a recessive pale green Arabidopsis mutant, bpg2-1 (Brz-insensitive-pale green 2-1) that showed reduced sensitivity to chlorophyll accumulation promoted by Brz in the light. BPG2 encodes a chloroplast-localized protein with a zinc finger motif and four GTP-binding domains that are necessary for normal chloroplast biogenesis. BPG2-homologous genes are evolutionally conserved in plants, green algae and bacteria. Expression of BPG2 is induced by light and Brz. Chloroplasts of the bpg2-1 mutant have a decreased number of stacked grana thylakoids. In bpg2-1 and bpg2-2 mutants, there was no reduction in expression of rbcL and psbA, but there was abnormal accumulation of precursors of chloroplast 16S and 23S rRNA. Chloroplast protein accumulation induced by Brz was suppressed by the bpg2 mutation. These results indicate that BPG2 plays an important role in post-transcriptional and translational regulation in the chloroplast, and is a component of BR signaling.

Brassinosteroid signalling

“…PAR1 and HFR1 bind to and inhibit PIF4 (Hao et al, 2012;Hornitschek et al, 2009), and therefore BR activation of PREs would lead to inhibition of PAR1 and HFR1 and to an increase in PIF4 activity (Hao et al, 2012). BR-mediated inhibition of chloroplast development is correlated with repression of the two GOLDEN 2-LIKE (GLK) transcription factors (GLK1 and GLK2), which are major regulators of nuclear genes encoding chloroplast proteins Waters et al, 2009;Yu et al, 2011), as well as of the nuclear-encoded chloroplast protein BRASSINAZOLE INSENSITIVE PALE GREEN2 (BPG2), which is required for the translation of chloroplast-encoded photosynthetic proteins (Komatsu et al, 2010).…”

Leaf Variegation of Thylakoid Formation1 Is Suppressed by Mutations of Specific σ-Factors in Arabidopsis

“…The transfer DNA insertion mutant of sig4 (Salk_146777) was identified from the Arabidopsis Biological Resource Center seed stocks. Other single mutants used in this study were previously described: thf1 (Wang et al, 2004), ys1 (Zhou et al, 2009), bpg2 (Komatsu et al, 2010), noa1/nos1 (Guo et al, 2003), sig1 (Lai et al, 2011), sig2 (Oh and Montgomery, 2013), sig3 (Zghidi et al, 2007), and sig5 (Tsunoyama et al, 2004).…”

“…To do this, we selected three virescent mutants (no-associated protein1 [noa1; Guo et al, 2003], yellow seedling1 [ys1; Zhou et al, 2009], and brz-insensitive-pale green2 [bpg2; Komatsu et al, 2010]) and constructed their double mutants with thf1. Similar to that previously reported, chloroplast development was slower in cotyledons and young leaves of 8-d-old ys1, noa1, and bpg2 seedlings compared with the wild type (Fig.…”

Abamine as a basis for new designs of regulators of strigolactone production

“…In addition, a mutation or targeted knockout of an individual gene in sets of paralogous genes encoding these biosynthetic inhibitors has few phenotypic effects as they are able to overcome such gene redundancy in many cases; therefore, the use of specific biosynthetic inhibitors in the study of plant biology is an alternative and valuable way to determine the physiological functions of endogenous substances. As was seen in the case of brassinosteroid biosynthesis inhibitors, [8][9][10][11] specific strigolactone biosynthesis inhibitors proved useful in functional studies of strigolactone biosynthesis and in assessments of the effect of strigolactone in plants. Moreover, strigolactone biosynthesis inhibitors may be useful in understanding the regulation of germination and infestation in parasitic weeds.…”