دكتوراه
العلوم والتقنية
University of Leeds
مجال التميز | تميز دراسي وبحثي |
البحوث المنشورة |
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البحث (1): | |
عنوان البحث: | Inhibitor-induced oxidation of the nucleus and cytosol in Arabidopsis thaliana: implications for organelle to nucleus retrograde signalling |
رابط إلى البحث: | https://royalsocietypublishing.org/doi/10.1098/rstb.2016.0392 |
تاريخ النشر: | 14/08/2017 |
موجز عن البحث: | Concepts of organelle-to-nucleus signalling pathways are largely based on genetic screens involving inhibitors of chloroplast and mitochondrial functions such as norflurazon, lincomycin (LINC), antimycin A (ANT) and salicylhydroxamic acid. These inhibitors favour enhanced cellular oxidation, but their precise effects on the cellular redox state are unknown. Using the in vivo reduction–oxidation (redox) reporter, roGFP2, inhibitor-induced changes in the glutathione redox potentials of the nuclei and cytosol were measured in Arabidopsis thaliana root, epidermal and stomatal guard cells, together with the expression of nuclear-encoded chloroplast and mitochondrial marker genes. All the chloroplast and mitochondrial inhibitors increased the degree of oxidation in the nuclei and cytosol. However, inhibitor-induced oxidation was less marked in stomatal guard cells than in epidermal or root cells. Moreover, LINC and ANT caused a greater oxidation of guard cell nuclei than the cytosol. Chloroplast and mitochondrial inhibitors significantly decreased the abundance of LHCA1 and LHCB1 transcripts. The levels of WHY1, WHY3 and LEA5 transcripts were increased in the presence of inhibitors. Chloroplast inhibitors decreased AOXA1 mRNA levels, while mitochondrial inhibitors had the opposite effect. Inhibitors that are used to characterize retrograde signalling pathways therefore have similar general effects on cellular redox state and gene expression. |
البحث (2): | |
عنوان البحث: | Ascorbate-mediated regulation of growth, photoprotection, and photoinhibition in Arabidopsis thaliana |
رابط إلى البحث: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5961140/ |
تاريخ النشر: | 03/05/2018 |
موجز عن البحث: | The requirements for ascorbate for growth and photosynthesis were assessed under low (LL; 250 µmol m–2 s–1) or high (HL; 1600 µmol m–2 s–1) irradiance in wild-type Arabidopsis thaliana and two ascorbate synthesis mutants (vtc2-1 and vtc2-4) that have 30% wild-type ascorbate levels. The low ascorbate mutants had the same numbers of leaves but lower rosette area and biomass than the wild type under LL. Wild-type plants experiencing HL had higher leaf ascorbate, anthocyanin, and xanthophyll pigments than under LL. In contrast, leaf ascorbate levels were not increased under HL in the mutant lines. While the degree of oxidation measured using an in vivo redox reporter in the nuclei and cytosol of the leaf epidermal and stomatal cells was similar under both irradiances in all lines, anthocyanin levels were significantly lower in the low ascorbate mutants than in the wild type under HL. Differences in the photosynthetic responses of vtc2-1 and vtc2-4 mutants were observed. Unlike vtc2-1, the vtc2-4 mutants had wild-type zeaxanthin contents. While both low ascorbate mutants had lower levels of non-photochemical quenching of chlorophyll a fluorescence (NPQ) than the wild type under HL, qPd values were greater only in vtc2-1 leaves. Ascorbate is therefore essential for growth but not for photoprotection. |
البحث (3): | |
عنوان البحث: |
Papain-like cysteine proteases are required for the regulation of photosynthetic gene expression and acclimation to high light stress |
رابط إلى البحث: | https://academic.oup.com/jxb/advance-article-abstract/doi/10.1093/jxb/erab101/6158364?redirectedFrom=fulltext |
تاريخ النشر: | 04/03/2021 |
موجز عن البحث: | Chloroplasts are considered to be devoid of cysteine proteases. Using transgenic Arabidopsis lines expressing the rice cystatin, oryzacystatin I (OC-I), in the chloroplasts (PC lines) or cytosol (CYS lines), we explored the hypothesis that cysteine proteases regulate photosynthesis. The CYS and PC lines flowered later than the wild type (WT) and accumulated more biomass after flowering. In contrast to the PC rosettes, which accumulated more leaf chlorophyll and carotenoid pigments than the WT, the CYS lines had lower amounts of leaf pigments. High-light-dependent decreases in photosynthetic carbon assimilation and the abundance of the Rubisco large subunit protein, the D1 protein, and the phosphorylated form of D1 proteins were attenuated in the CYS lines and reversed in the PC lines relative to the WT. However, the transgenic lines had higher amounts of LHC, rbcs, pasbA, and pasbD transcripts than the WT, and also showed modified chloroplast to nucleus signalling. We conclude that cysteine proteases accelerate the reconfiguration of the chloroplast proteome after flowering and in response to high-light stress. Inhibition of cysteine proteases, such as AtCEP1, slows chloroplast protein degradation and stimulates photosynthetic gene expression and chloroplast to nucleus signalling, enhancing stress tolerance traits. |
المؤتمرات العلمية |
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المؤتمر (1): | |
عنوان المؤتمر: | GARNet2018: a Plant Science Showcase |
تاريخ الإنعقاد: | 18-19/09/2018 |
مكان الإنعقاد: | York – UK |
طبيعة المشاركة: | |
عنوان المشاركة: |
Expression of the rice cystatin, oryzacystatin-I (OC-I) influences the shoot phenotype in Arabidopsis |
ملخص المشاركة: | Plants contain large numbers of proteases that fulfill a wide range of functions, including the regulation of metabolism, enzyme activation, transcription factor cleavage, and removal of membrane receptors. The in vivo activities of proteases is, in many cases, controlled by endogenous protease inhibitors. Cysteine protease inhibitors, which are called cystatins or phytocystatins, are have been implicated in the control of stress tolerance and lifespan, but their precise functions remain poorly characterized. Oryzacystatin I (OC-I), which was first identified in rice seeds (Oryza sativa L. japonica), is perhaps the best-characterised phytocystatin. This protein has been expressed in a range of transgenic plants to study the functions of cysteine protease activities. However, in most studies, OC-I expression was not targetted to specific organelles. Since no cysteine proteases have been identified in chloroplasts, a key question concerns how OC-I expression alters the abundance of chloroplast proteins and enhances the Rubisco activity during age-related or stress-induced senescence. Transgenic Arabidopsis lines that express OC-I either in the cytosol (CYS) or in the chloroplasts (PC) have already been produced to address this question. The PC lines (PC2, PC7, and PC9) showed a slower growth phenotype with greater accumulation of shoot biomass. These lines also accumulated significantly more leaf chlorophyll and carotenoid pigments than the wild type at the later stages of shoot development. These data show that OC-I dependent inhibition of papain-like cysteine proteases has significant effects on shoot growth and development. Moreover, the findings regarding the targeting of OC-I to chloroplasts suggest that cysteine proteases influence chloroplast processes that exert a wide range of effects on shoot development. |
الرابط: | https://www.garnetcommunity.org.uk/sites/default/files/GARNet2018_Abstract_book_Online.pdf |