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.
Arabidopsis plastidic HSP90C is an HSP90 family molecular chaperone that is required for chloroplast development and function. To understand the mechanism of action of HSP90C within the chloroplast, we conducted a yeast two-hybrid screening and revealed it interacts directly with the photosystem II extrinsic protein PsbO1, which performs a canonical function in the thylakoid lumen. To understand the biological significance of HSP90C-PsbO1 interaction, we investigated the role of HSP90C in modulating the stromal and thylakoid distribution of PsbO1GFP fusion protein. Fusion to GFP significantly delays the PsbO1 thylakoid transport and induces a variegation phenotype. Overexpression of HSP90C promotes the thylakoid distribution of PsbO1GFP and alleviates the leaf variegation. By tracking the chloroplast maturation during photomorphogenesis, we observed PsbO1GFP tends to form distinct fluorescent clusters within the stroma with delayed thylakoid membrane biogenesis, while HSP90C overexpression corrects these adverse effects. We also demonstrated that active HSP90C function is specifically required for stable accumulation of mature PsbO1GFP in thylakoid by using specific inhibitor geldanamycin. This study therefore not only identified novel HSP90C interactors, but also reports for the first time that PsbO1 enroute from the cytoplasm to thylakoid lumen is tightly regulated by the HSP90C chaperone complex in plastid stroma; whereas the proper HSP90C homeostasis is also critical for chloroplast maturation and function.
Rosa canina (wild rose, bush, bramble, dog rose, rosehip) is a shrub commonly encountered in the wild flora of Romania, spread from the coast up to altitudes of 1200 m (1700), with low requirements to pedoclimatic factors. From this species are used the false-fruits (Cynosbati fructus) mature, dried, harvested from wild flora or cultures, with food and therapeutic importance, due to their multiple properties, but mostly because of its high content of vitamin C. In this way, it were studied the germoplasm sources existent in some areas of Oltenia (Romania) to identify valuable biotypes from biochemically and technologically point of view. The results indicate a high and very high variability of the analyzed parameters. Thus, the content of TSS was recorded between 10% (B2) and 18% (M1), vitamin C varied from 53mg/100g (B3) to 563 mg /100g to populations (S1 , S3) and acidity from 1.4% (B3) to 3.6% (M4). Recorded values for the mass of 100 fruit, between 117g (A1) and 286g (B3 and T4) and the percentage of pulp/100g fruit ranged from 49.2 (M1) and 66.5 (T1).
The present study investigates the cytogenetic effects of the fungicide Royal Flo on mitotic cell division in maize (Zea mays L.) root cells. The maize grains were treated with various fungicide concentrations (50, 70, and 80%) for 20, 24 and 48 h exposure times. The results obtained indicate that the fungicide Royal Flo had some cytogenetic effects, by reducing the mitotic index and inducing various cytologic and chromosomal anomalies. These effects manifested differently, their intensity being proportional to the concentration and exposure time. The most frequent chromosomal anomalies were bridges, fragments and binucleated cells, but sticky chromosomes, rings chromosomes and cells with a micronucleus have also been seen. This study proves that the fungicide Royal Flo, even when administered in smaller quantities than generally recommended, reduces the germination and the mitotic index of maize cells and induces a large number of chromosomal anomalies, which suggests its toxic, mutagenic potential. Consequently, we should identify the optimal concentrations for each agricultural species, so that the efficacy of the fungicide does not diminish and, at the same time, its cytogenotoxic potential is kept low.
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