The SLOW GROWTH3 Pentatricopeptide Repeat Protein Is Required for the Splicing of Mitochondrial NADH Dehydrogenase Subunit7 Intron 2 in Arabidopsis

Abstract

Mitochondria play an important role in maintaining metabolic and energy homeostasis in the cell. In plants, impairment in mitochondrial functions usually has detrimental effects on growth and development. To study genes that are important for plant growth, we have isolated a collection of slow growth (slo) mutants in Arabidopsis (Arabidopsis thaliana). One of the slo mutants, slo3, has a significant reduction in mitochondrial complex I activity. The slo3 mutant has a four-nucleotide deletion in At3g61360 that encodes a pentatricopeptide repeat (PPR) protein. The SLO3 protein contains nine classic PPR domains belonging to the P subfamily. The small deletion in the slo3 mutant changes the reading frame and creates a premature stop codon in the first PPR domain. We demonstrated that the SLO3-GFP is localized to the mitochondrion. Further analysis of mitochondrial RNA metabolism revealed that the slo3 mutant was defective in splicing of NADH dehydrogenase subunit7 (nad7) intron 2. This specific splicing defect led to a dramatic reduction in complex I activity in the mutant as revealed by blue native gel analysis. Complementation of slo3 by 35S:SLO3 or 35S:SLO3-GFP restored the splicing of nad7 intron 2, the complex I activity, and the growth defects of the mutant. Together, these results indicate that the SLO3 PPR protein is a splicing factor of nad7 intron 2 in Arabidopsis mitochondria.

The MTL1 Pentatricopeptide Repeat Protein Is Required for Both Translation and Splicing of the Mitochondrial NADH DEHYDROGENASE SUBUNIT7 mRNA in Arabidopsis

“…S4). These very mild alterations could simply represent pleiotropic effects of the loss of complex I, as observed in several other complex I mutants (Haïli et al, 2013;Colas des Francs-Small et al, 2014;Hsieh et al, 2015), and do not support a direct role of MTL1 in the splicing of these introns. Oppositely, the 16-fold decrease of nad7 intron 2 splicing efficiency resulted in a measured 43 reduction in the accumulation level of nad7 mature mRNA ( Fig.…”

Dysfunctional mitochondria regulate the size of root apical meristem and leaf development in Arabidopsis

“…8 We used ethynyl deoxyuridine (EdU) staining to demonstrate that the slo3 mutant has significantly fewer proliferating cells than wild type (WT) in the primary root. 7 Since the modified nucleoside EdU is incorporated during DNA synthesis, those EdU-stained cells may represent dividing cells in the root apical meristem (RAM) during the treatment. Thus, these results suggest that the slow growth of slo3 is due to a reduction in meristem size and a decrease in cell production rate in the primary root.…”

“…6 Recently, we reported the characterization of another Arabidopsis slo mutant, slo3, which is similar to slo1 in growth phenotypes. 7 The SLO3 gene encodes a PPR protein of the P subfamily that is required for the splicing of nad7 intron 2 in Arabidopsis mitochondria. 7 The respiratory complex I activity is dramatically reduced in slo3, which may be responsible for the slow growth phenotypes of the mutant.…”

“…7 The SLO3 gene encodes a PPR protein of the P subfamily that is required for the splicing of nad7 intron 2 in Arabidopsis mitochondria. 7 The respiratory complex I activity is dramatically reduced in slo3, which may be responsible for the slow growth phenotypes of the mutant. 7 Although these molecular defects are sufficient to explain the retarded growth and delayed development in the slo3 mutant, still, how exactly dysfunctional mitochondria affect plant growth and development remain unclear.…”

Changes in the OXPHOS system in leaf and root mitochondria of Arabidopsis thaliana subjected to long-term sulphur deficiency

“…NAD7 and NAD4, showed dysfunction in Complex I formation (Gutierres et al 1997;Karpova and Newton 1999). Moreover, studies of several pentatricopeptide repeat protein (PPR) mutants have shown that all mitochondrial-encoded subunits are required for the proper assembly of the respiratory chain complexes (Colas des Francs-Small et al 2014;Colas des Francs-Small and Small 2014;Hsieh et al 2015).…”