Fen Edebiyat Fakültesi / Faculty of Letters and Science

Permanent URI for this collectionhttps://hdl.handle.net/11727/1396

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    Role Of Sulfur Metabolism In Acquiring Of Boron Tolerance In Arabidopsis Thaliana
    (TURKISH JOURNAL OF BOTANY, 2024) Yirmibes, Seda; Kayihan, Ceyhun; Cicek, Nuran; Ekmekci, Yasemin
    The purpose of this study was to assess whether sulfate treatment (pre- and combined) caused changes in the tolerance against boron (B) toxicity in Arabidopsis thaliana at the physiological, biochemical, and molecular levels. Germinated plants were grown in a controlled climate chamber (22 +/- 1 degrees C temperature, 16/8 s photoperiod, 200 mu mol m -2 s -1 light intensity and 50%-60% humidity) for 12 days. The sulfate pretreatment groups (PS-3B and PS-5B) were then transferred to nutrient medium containing Mg2SO4- type sulfate for 3 days. Afterward, they were transferred to petri dishes containing different boron concentrations (3 and 5 mM H3BO3), along with the nonpretreatment and combined (S+3B and S+5B) treatment groups, and exposed to boron toxicity for 10 days. The leaf area, plant biomass, and total chlorophyll content decreased significantly depending on the accumulation of B. Toxic levels of B adversely affected the structure and functionality of the photosynthetic apparatus. Changes were seen in the specific and phenomenological energy fluxes, quantum yields, and efficiency of the photosystem II (PSII) donor and acceptor sides. These changes led to decreases in the photosynthetic performance of the plants. Although B toxicity adversely affected the integrity of the membrane and the amount of photosynthetic pigment in the antenna and reaction centers (RCs), this effect was not at a level that completely blocked the functionality of the photosystems, and this negative effect was alleviated with the sulfate treatment. The increases in the antioxidant enzyme activities (especially peroxidase) and phenolic compounds with the sulfate treatment may have provided tolerance against toxicity and oxidative damage by regulating the defense systems. Moreover, B toxicity affected the relative expression of genes related to sulfate uptake, transport, and sulfur metabolism. In fact, the genes of sulfate transporters ( SULTR ); SULTR3;1, SULTR3;3, and SULTR3;5 were more expressed in PS-B group. The glutamate cysteine ligase (GSH1) and glutathione synthetase 1 (GSH2) relative gene expressions were increased in the treatment groups, indicating induced glutathione metabolism. In conclusion, plants may have acquired tolerance against B toxicity by assimilating sulfate, especially that provided by sulfate pretreatment.
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    The involvement of the induction of anthocyanin biosynthesis and transport in toxic boron responsive regulation in Arabidopsis thaliana
    (2021) Kayihan, Ceyhun; 0000-0003-1684-4147; AAW-8352-2021
    Recently, boron (B) has been found to form a complex with anthocyanin, which could be evidence for the B tolerance mechanisms that reduce free B in the leaf tissues of plants. However, the molecular mechanism of anthocyanin biosynthesis and transport has not been satisfactorily elucidated in plants exposed to toxic B. Therefore, the changes in expression levels of some of the phenylpropanoid pathway genes, early and late flavonoid biosynthetic genes, and transcription factors related to anthocyanin biosynthesis and transport were determined in Arabidopsis thaliana under B toxicity. Accordingly, 1 mM boric acid treatment did not cause any significant change in the expression levels of anthocyanin biosynthesis genes such as PAL1, PAL2, C4H, 4CL3, CHS, ANS and transcription factors such as MYBD and TT8 in Arabidopsis thaliana. However, 3 mM boric acid treatment induced the expression levels of anthocyanin biosynthesis genes such as C4H, 4CL3 and transcription factors including MYB75, MYB114 and anthocyanin transporter genes such as TT13 and TT19. In addition to B-anthocyanin, B-anthocyanins conjugated with glutathione (GSH) complexes can also participate in the internal B tolerance mechanism in plants. Therefore, the direct role of the B-anthocyanin complex without GSH conjugation needs to be determined. For this purpose, anthocyanin accumulation was determined in slim1 mutant Arabidopsis thaliana exposed to excess B because SLIM1 transcription factor activates sulfate acquisition for S assimilation, which generates cysteine, the substrate for GSH. Accordingly, it was gradually increased through increasing toxic B levels in both wild type (WT) and slim1 mutant plants. slim1 mutant had more anthocyanin accumulation than WT under control and all toxic B conditions. In conclusion, increases in expression levels of MYB75, MYB114, TT13, TT19 and in anthocyanin level in slim1 mutant in response to increased toxic B levels showed that anthocyanins may play a primary role in B tolerance in plants.
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    Moderate level of toxic boron causes differential regulation of microRNAs related to jasmonate and ethylene metabolisms in Arabidopsis thaliana
    (2019) Kayihan, Doga Selin; Kayihan, Ceyhun; Ciftci, Yelda Ozden; 0000-0003-1684-4147; Q-4515-2016
    Earlier our colleagues detected that the genes related to jasmonate (JA), ethylene, and cell wall modification were significantly regulated under boron (B) toxicity in wheat. Determination of regulation mechanisms of these novel genes under B toxicity is very important in Arabidopsis thaliana as a model plant. As key regulators, the microRNAs (miRNAs) regulate gene expression at the posttranscriptional level and respond to numerous abiotic stresses in plants. In this study, expression levels of miRNAs such as miR159, miR172, miR319, and miR394 targeting JA and ethylene-related transcription factors and also miR397 targeting laccase were determined in Arabidopsis thaliana under toxic B conditions. Stem-loop quantitative reverse transcription polymerase chain reaction was used to amplify mature miRNAs for expression analyses. Expression levels of miRNAs targeting transcription factors related to JA and ethylene metabolisms were induced remarkably in moderate B toxicity (condition 1B) but not in severe B toxicity (condition 3B). Most remarkable regulations were obtained in miR172 and miR319 in Arabidopsis thaliana. Expression level of miR397 did not remarkably change under B toxicity, indicating a lack of posttranscriptional regulation of laccase related to cell wall modification. Moreover, miRNAs targeting transcription factors related to JA and ethylene metabolisms might be oxidative stress-adaptive responses of Arabidopsis to B toxicity.