A tetratricopeptide repeat domain‐containing protein SSR1 located in mitochondria is involved in root development and auxin polar transport in Arabidopsis

Abstract

These authors contributed equally to this work. ‡ These authors share senior authorship. SUMMARYAuxin polar transport mediated by a group of Pin-formed (PIN) transporters plays important roles in plant root development. However, the mechanism underlying the PIN expression and targeting in response to different developmental and environmental stimuli is still not fully understood. Here, we report a previously uncharacterized gene SSR1, which encodes a mitochondrial protein with tetratricopeptide repeat (TPR) domains, and show its function in root development in Arabidopsis thaliana. In ssr1-2, a SSR1 knock-out mutant, the primary root growth was dramatically inhibited due to severely impaired cell proliferation and cell elongation. Significantly lowered level of auxin was found in ssr1-2 roots by auxin measurement and was further supported by reduced expression of DR5-driven reporter gene. As a result, the maintenance of the root stem cell niche is compromised in ssr1-2. It is further revealed that the expression level of several PIN proteins, namely, PIN1, PIN2, PIN3, PIN4 and PIN7, were markedly reduced in ssr1-2 roots. In particular, we showed that the reduced protein level of PIN2 on cell membrane in ssr1-2 is due to impaired retrograde trafficking, possibly resulting from a defect in retromer sorting system, which destines PIN2 for degradation in vacuoles. In conclusion, our results indicated that SSR1 is functioning in root development in Arabidopsis, possibly by affecting PIN protein expression and subcellular targeting.

HLB1 Is a Tetratricopeptide Repeat Domain-Containing Protein That Operates at the Intersection of the Exocytic and Endocytic Pathways at the TGN/EE in Arabidopsis

“…Other TPR domain-containing proteins among the 147 in Arabidopsis, including SHORT AND SWOLLEN ROOT1 and MET1, localize to mitochondria and chloroplasts, respectively, consistent with their functions in oxidative stress-mediated root development and in the assembly of the photosynthetic apparatus (Bhuiyan et al, 2015;Zhang et al, 2015). The TPR protein CLUMPED CHLOROPLAST1 (CLMP1) localizes to distinct foci in the cytoplasm.…”

Nuclear Prohibitin3 Maintains Genome Integrity and Cell Proliferation in the Root Meristem through Minichromosome Maintenance 2

“…2B). The deficiency of QC cells in phb3 was further confirmed by an altered expression pattern and lower expression level of WOX5pro::GFP (green fluorescent protein), which is another QC-specific marker (Blilou et al, 2005;Ji et al, 2015;Zhang et al, 2015), compared with that in the wild type ( Fig. 2C).…”

“…salk.edu): phb3-ko (PHB3-knock out mutant, SALK_020707) and phb3-3 (a mutation that resulted in the conversion of Gly-37 to an Asp; Wang et al, 2010). The following types of marker lines and mutant were used: CycB1;1:GUS ; CDKA;1:GUS (Menges et al, 2002;Vandepoele et al, 2002); WOX5pro: GFP (Blilou et al, 2005;Ji et al, 2015;Zhang et al, 2015); QC25, QC46, and QC18 (Sabatini et al, 2003); JO571:GFP (Petersson et al, 2015); J2341:GFP (Zhou et al, 2010); DR5pro:GFP (Ulmasov et al, 1997); DR5:GUS (Ulmasov et al, 1997); PIN1pro:PIN1:GFP (Benková et al, 2003); PIN2pro:PIN2:GFP (Blilou et al, 2005); shr-1 (Benfey et al, 1993); scr-1(Di Laurenzio et al, 1996); plt1-4 plt2-2 (Aida et al, 2004); SHRpro:SHR-GFP; SCRpro:SCR-GFP (Aida et al, 2004;Galinha et al, 2007); ASA1pro:GUS (Stepanova et al, 2005); and PLT1pro: PLT1:YFP and PLT2pro:PLT2:YFP (Galinha et al, 2007).…”

“…Only the area with fluorescence was taken into account. The fluorescence intensities of the wild type were taken as 100%, and those samples that are needed to quantify are presented as relative values (Zhang et al, 2015). Three independent experiments were performed, and the statistical significance was evaluated by Student's t test analysis.…”

A novel tetratricopeptide repeat protein, WHITE TO GREEN1, is required for early chloroplast development and affects RNA editing in chloroplasts

“…The albino phenotype with chloroplast biogenesis deficiency is reminiscent of some mutants with defective plastid RNA editing ( Chateigner-Boutin et al , 2008 , Yu et al , 2009 , Zhou et al , 2009 , Takenaka et al , 2012 , Sun et al , 2015 , Yap et al , 2015 , Zhang et al , 2015 ). We therefore compared the states of chloroplast RNA editing in 18-day-old wild-type plants, wtg1 mutants, and the complemented transgenic line by bulk sequencing.…”