var2 genetic suppressors

The Arabidopsis variegation2 (var2) mutant, displaying a conspicuous green and white sectoring phenotype, is one of the most well-characterized variegation mutants and is the caused by mutations in VAR2, which encodes a subunit of the FtsH metalloprotease complex situated in the chloroplast thylakoid membranes. FtsH proteins mediate a myriad of processes in plants, the most prominent one being the turnover of photosystem II reaction center D1 protein. The Rodermel lab is interested in using the unique variegation phenotype of var2 mutant as a tool to study the mechanism of variegation and the regulation of chloroplast biogenesis. To this end, our lab has carried out second-site var2 genetic suppressor screens to obtain mutants with non-variegation phenotype despite the var2 mutant background. Previous work with several var2 suppressors carried out in our lab and others\u27 has uncovered an unexpected link between var2 variegation and chloroplast translation. A number of suppressor lines have defects in chloroplast rRNA processing and/or chloroplast translation. My research has been primarily focused on two var2 suppressor lines, 004-003 (var2-5 svr7-1) and TAG-11 (var2-5 svr3-1). The molecular cloning of the two suppressor genes revealed that SVR7 is a chloroplast PPR (Pentatricopeptide Repeat) protein that might function in nucleic acids binding whereas SVR3 is a chloroplast homolog of the prokaryotic TypA translation elongation factor. Consistent with the link between var2 and chloroplast translation, both mutant lines have distinct chloroplast rRNA processing defects. Interestingly, I also found that var2 and svr3 single mutants are both chilling sensitive and that they display a pronounced chlorosis phenotype at low temperatures. These findings reinforced the known relationship between chloroplast translation and chilling stress and also the connection between VAR2 function and chloroplast translation. Extending from the var2 suppressor work , I also carried out research that led to the identification of a putative chloroplast protease, VirX, and the generation a var2-4 near isogenic line in the Landsberg erecta ecotype background

A var2 leaf variegation suppressor locus, SUPPRESSOR OF VARIEGATION3, encodes a putative chloroplast translation elongation factor that is important for chloroplast development in the cold

<p>Abstract</p> <p>Background</p> <p>The Arabidopsis <it>var2 </it>mutant displays a unique green and white/yellow leaf variegation phenotype and lacks VAR2, a chloroplast FtsH metalloprotease. We are characterizing second-site <it>var2 </it>genetic suppressors as means to better understand VAR2 function and to study the regulation of chloroplast biogenesis.</p> <p>Results</p> <p>In this report, we show that the suppression of <it>var2 </it>variegation in suppressor line <it>TAG-11 </it>is due to the disruption of the <it>SUPPRESSOR OF VARIEGATION3 </it>(<it>SVR3</it>) gene, encoding a putative TypA-like translation elongation factor. SVR3 is targeted to the chloroplast and <it>svr3 </it>single mutants have uniformly pale green leaves at 22°C. Consistent with this phenotype, most chloroplast proteins and rRNA species in <it>svr3 </it>have close to normal accumulation profiles, with the notable exception of the Photosystem II reaction center D1 protein, which is present at greatly reduced levels. When <it>svr3 </it>is challenged with chilling temperature (8°C), it develops a pronounced chlorosis that is accompanied by abnormal chloroplast rRNA processing and chloroplast protein accumulation. Double mutant analysis indicates a possible synergistic interaction between <it>svr3 </it>and <it>svr7</it>, which is defective in a chloroplast pentatricopeptide repeat (PPR) protein.</p> <p>Conclusions</p> <p>Our findings, on one hand, reinforce the strong genetic link between VAR2 and chloroplast translation, and on the other hand, point to a critical role of SVR3, and possibly some aspects of chloroplast translation, in the response of plants to chilling stress.</p

A New Allele of the SPIKE1 Locus Reveals Distinct Regulation of Trichome and Pavement Cell Development and Plant Growth

The single-celled trichomes of Arabidopsis thaliana have long served as an elegant model for elucidating the mechanisms of cell differentiation and morphogenesis due to their unique growth patterns. To identify new components in the genetic network that governs trichome development, we carried out exhaustive screens for additional Arabidopsis mutants with altered trichome morphology. Here, we report one mutant, aberrantly branched trichome1-1 (abt1-1), with a reduced trichome branching phenotype. After positional cloning, a point mutation in the SPIKE1 (SPK1) gene was identified in abt1-1. Further genetic complementation experiments confirmed that abt1-1 is a new allele of SPK1, so abt1-1 was renamed as spk1-7 according to the literatures. spk1-7 and two other spk1 mutant alleles, covering a spectrum of phenotypic severity, highlighted the distinct responses of developmental programs to different SPK1 mutations. Although null spk1 mutants are lethal and show defects in plant stature, trichome and epidermal pavement cell development, only trichome branching is affected in spk1-7. Surprisingly, we found that SPK1 is involved in the positioning of nuclei in the trichome cells. Lastly, through double mutant analysis, we found the coordinated regulation of trichome branching between SPK1 and two other trichome branching regulators, ANGUSTIFOLIA (AN) and ZWICHEL (ZWI). SPK1 might serve for the precise positioning of trichome nuclei, while AN and ZWI contribute to the formation of branch points through governing the cMTs dynamics. In summary, this study presented a fully viable new mutant allele of SPK1 and shed new light on the regulation of trichome branching and other developmental processes by SPK1

Mortality among People Living with HIV and AIDS in China: Implications for Enhancing Linkage.

To assess the patterns and predictors of AIDS-related mortality and identify its correlates among adult people living with HIV/AIDS (PLWHA) in China, a retrospective record-based cohort study was conducted among 18 years or older PLWHA, who had at least one follow up reported to the national database between January-1989 and June-2012. Cumulative Incidence Function was used to calculate AIDS-related mortality rate. Gray's test was used to determine the variation in cumulative incidence across strata. The Fine and Gray model was used to measure the burden of cumulative incidence of AIDS-related mortality and strength of its association with potential correlates. Among 375,629 patients, 107,634 died during study period, of which 54,759 (50.87%) deaths were AIDS-related. Cumulative mortality rates of AIDS-related death at one, two, five, 10 and 15 years post-diagnosis were 5.7%, 8.2%, 14.3%, 22.9% and 30.9%, respectively. Among PLWHA, male gender, ethnic minority and having AIDS were associated with significantly higher mortality. Further, homosexual transmission, being on ART and increasing CD4-testing frequency were associated with lower mortality. To reduce mortality among PLWHA, efficient interventions targeting males, ethnic minority, heterosexually infected and AIDS patients should be combined with immunologic monitoring, enhancement of coverage of HIV-testing and ART

var2 genetic suppressors

The Arabidopsis variegation2 (var2) mutant, displaying a conspicuous green and white sectoring phenotype, is one of the most well-characterized variegation mutants and is the caused by mutations in VAR2, which encodes a subunit of the FtsH metalloprotease complex situated in the chloroplast thylakoid membranes. FtsH proteins mediate a myriad of processes in plants, the most prominent one being the turnover of photosystem II reaction center D1 protein. The Rodermel lab is interested in using the unique variegation phenotype of var2 mutant as a tool to study the mechanism of variegation and the regulation of chloroplast biogenesis. To this end, our lab has carried out second-site var2 genetic suppressor screens to obtain mutants with non-variegation phenotype despite the var2 mutant background. Previous work with several var2 suppressors carried out in our lab and others' has uncovered an unexpected link between var2 variegation and chloroplast translation. A number of suppressor lines have defects in chloroplast rRNA processing and/or chloroplast translation. My research has been primarily focused on two var2 suppressor lines, 004-003 (var2-5 svr7-1) and TAG-11 (var2-5 svr3-1). The molecular cloning of the two suppressor genes revealed that SVR7 is a chloroplast PPR (Pentatricopeptide Repeat) protein that might function in nucleic acids binding whereas SVR3 is a chloroplast homolog of the prokaryotic TypA translation elongation factor. Consistent with the link between var2 and chloroplast translation, both mutant lines have distinct chloroplast rRNA processing defects. Interestingly, I also found that var2 and svr3 single mutants are both chilling sensitive and that they display a pronounced chlorosis phenotype at low temperatures. These findings reinforced the known relationship between chloroplast translation and chilling stress and also the connection between VAR2 function and chloroplast translation. Extending from the var2 suppressor work , I also carried out research that led to the identification of a putative chloroplast protease, VirX, and the generation a var2-4 near isogenic line in the Landsberg erecta ecotype background.</p

Long-Term Application of Bio-Compost Increased Soil Microbial Community Diversity and Altered Its Composition and Network

The influence of bio-compost on the diversity, composition and structure of soil microbial communities is less understood. Here, Illumina MiSeq sequencing and a network analysis were used to comprehensively characterize the effects of 25 years of bio-compost application on the microbial diversity of soil and community composition. High dosages of bio-compost significantly increased the bacterial and fungal richness. The compositions of bacterial and fungal communities were significantly altered by bio-compost addition. Bio-compost addition enriched the relative abundance of beneficial microorganisms (such as Sphingomonas, Acidibacter, Nocardioides, etc.) and reduced the relative abundance of harmful microorganisms (such as Stachybotrys and Aspergillus). Electrical conductivity, soil organic matter and total phosphorus were the key factors in shaping soil microbial community composition. The bacterial network was more complex than fungal network, and bacteria were more sensitive to changes in environmental factors than fungi. Positive interactions dominated both the bacterial and fungal networks, with stronger positive interactions found in the bacterial network. Functional prediction suggested that bio-composts altered the soil bacterial-community metabolic function with respect to carbon, nitrogen and phosphorus cycles and fungal community trophic modes. In conclusion, suitable bio-compost addition is beneficial to the improvement of soil health and crop quality and therefore the sustainability of agriculture

New insights into the functions and regulations of MAP215/MOR1 and katanin, two conserved microtubule-associated proteins in Arabidopsis

Plant microtubules (MTs) form highly dynamic and distinct arrays throughout the cell cycle and are essential for cell and organ morphogenesis. A plethora of microtubule associated-proteins (MAPs), both conserved and plant-specific, ensure the dynamic response of MTs to internal and external cues. The MAP215 family MT polymerase/nucleation factor and the MT severing enzyme katanin are among the most conserved MAPs in eukaryotes. Recent studies have revealed unexpected functional and physical interactions between MICROTUBULE ORGANIZATION 1 (MOR1), the Arabidopsis homolog of MAP215, and KATANIN 1 (KTN1), the catalytic subunit of katanin. In this minireview, we provide a short overview on current understanding of the functions and regulations of MOR1 and katanin in cell morphogenesis and plant growth and development

An Arabidopsis Pentatricopeptide Repeat Protein, SUPPRESSOR OF VARIEGATION7, Is Required for FtsH-Mediated Chloroplast Biogenesis1[W][OA]

The Arabidopsis (Arabidopsis thaliana) yellow variegated2 (var2) mutant has green- and white-sectored leaves due to loss of VAR2, a subunit of the chloroplast FtsH protease/chaperone complex. Suppressor screens are a valuable tool to gain insight into VAR2 function and the mechanism of var2 variegation. Here, we report the molecular characterization of 004-003, a line in which var2 variegation is suppressed. We found that the suppression phenotype in this line is caused by lack of a chloroplast pentatricopeptide repeat (PPR) protein that we named SUPPRESSOR OF VARIEGATION7 (SVR7). PPR proteins contain tandemly repeated PPR motifs that bind specific RNAs, and they are thought to be central regulators of chloroplast and mitochondrial nucleic acid metabolism in plants. The svr7 mutant has defects in chloroplast ribosomal RNA (rRNA) processing that are different from those in other svr mutants, and these defects are correlated with reductions in the accumulation of some chloroplast proteins, directly or indirectly. We also found that whereas var2 displays a leaf variegation phenotype at 22°C, it has a pronounced chlorosis phenotype at 8°C that is correlated with defects in chloroplast rRNA processing and a drastic reduction in chloroplast protein accumulation. Surprisingly, the cold-induced phenotype of var2 cannot be suppressed by svr7. Our results strengthen the previously established linkage between var2 variegation and chloroplast rRNA processing/chloroplast translation, and they also point toward the possibility that VAR2 mediates different activities in chloroplast biogenesis at normal and chilling temperatures