A protein related to prokaryotic UMP kinases is involved in psaA/B transcript accumulation in Arabidopsis

Abstract

Dpt1 (defect in p saA/B transcript accumulation 1) is a novel photosystem (PS) I mutant in Arabidopsis. dpt1 mutants fail to grow photoautotrophically, and are impaired in the accumulation of psaA/B transcripts while the transcript levels for the remaining PSI subunits, for subunits of the PSII, the cyt-b ( 6 )/f-complex, and the ribulose-1,5-bisphosphate carboxylase are comparable to the wild type. In-organello run-on transcription assays demonstrate that the lower psaA/B transcript abundance in dpt1-1 is not caused by the inability to transcribe the psaA/psaB/rps14 operon. psaA/B transcripts in the mutant are associated with polyribosomes and translated. Thus, the mutation affects post-transcriptional processes specific for psaA/B. The dpt1 gene was isolated by map-based cloning. The protein is localized in the stroma of the chloroplast and exhibits striking similarities to UMP kinases of prokaryotic origin. Our results show that the nuclear encoded protein Dpt1 is essential for retaining photosynthetic activity in higher plant chloroplasts and involved in post-transcriptional steps of psaA/B transcript accumulation. We discuss that Dpt1 may be a bifunctional protein that couples the pyrimidine metabolism to the photosynthetic electron transport.

Modified Clp Protease Complex in the ClpP3 Null Mutant and Consequences for Chloroplast Development and Function in Arabidopsis

“…PPR protein SVR7 was identified as a suppressor of the FTSH2 protease VAR2 and has a chloroplast ribosomal RNA phenotype (Liu et al, 2011a). Uridylate kinase is involved in posttranscriptional steps of psaA/psaB transcript accumulation (Hein et al, 2009). Thus, loss of Clp protease function also impacts RNA metabolism.…”

The Arabidopsis nox Mutant Lacking Carotene Hydroxylase Activity Reveals a Critical Role for Xanthophylls in Photosystem I Biogenesis

“…Some of the available PsaA/B mutants are either defective in the transcription of the psaA-psaB-rps14 operon (Hein et al, 2009) or in its stability ; others are impaired in the translation of the dimeric complex or cannot accumulate a stable heterodimer (Stöckel et al, 2006;Albus et al, 2010) or are affected in intron splicing of chloroplast mRNAs, including those encoding molecular chaperone-like complexes, such as Ycf3 (Landau et al, 2009;Ye et al, 2012); others are defective in the stable assembly of several [4Fe-4S] cluster-containing complexes of chloroplasts, including the PsaA/ B dimer (Schwenkert et al, 2010).…”

Photosystem I: Its biogenesis and function in higher plants

“…Only massive reductions in the abundance of the polycistronic psaA-psaB-rps14 transcript (to 10% of wild-type levels) result in reduced PSI accumulation Hein et al, 2009). These observations are in line with data obtained in Chlamydomonas, where a repression in plastid genome copy number and mRNA accumulation by antibiotic treatments reduces photosynthetic complex contents only, when both are repressed to less than 10% of normal levels (Eberhard et al, 2002).…”