Expression Of miR398 Research Articles

Identification of MiR398 and Its Regulatory Roles in Terpenoid Biosynthesis of Persicaria odorata

Persicaria odorata is an herbaceous plant with antifungal and antibacterial properties. The plant produces secondary metabolites, including phenols, sulphur-containing compounds and terpenoids, in response to biotic and abiotic stresses. Terpenoids in P. odorata are synthesized through the mevalonate (MVA) and the methylerythritol phosphate (MEP) pathways. 1-deoxy-D-xylulose-5phosphate isomerase (DXR) is a rate-limiting enzyme in the MEP pathway and may be regulated by microRNA (miRNA) miR398. There is a lack of evidence showing miR398 regulation in terpenoid biosynthesis in P. odorata through DXR-targeting. The study aimed to verify the stem-loop structure of miR398 and analyse its expression towards the target gene, DXR, in treated and control P. odorata. RNA was quantified and qualitatively analysed using a Nanodrop spectrophotometer and agarose gel electrophoresis. The stem loop of miR398 was verified using reverse transcriptase PCR (RT-PCR) and agarose gel electrophoresis. The expression of miR398 and DXR was compared between control and treated samples. Treated leaves were punctured with needles and left for 48h before harvest. Gene expressions were quantified and normalised using reference genes. The stem-loop structure of miR398 was confirmed, despite possible primer mismatches and unspecific binding. This step was essential before comparing and assessing the gene expression of miR398 and DXR. A decrease in abundance of miR398 whereas in increase in abundance was in the treated sample compared to the control sample indicating that miR398 negatively regulated DXR under stress conditions, suggesting an increase in terpenoid synthesis as a defence mechanism. DXR acts as a rate-limiting enzyme in the MEP metabolic pathway. Further studies are needed to quantify the effects of miR398 on terpenoid biosynthesis after wounding in P. odorata.

Molecular manipulations of miR398 increase rice grain yield under different conditions.

Rice miR398 targets two stress-tolerant genes, CSD1-2 (Cu/Zn Superoxide Dismutases1-2) and CCS (copper chaperone of CSD), which usually boost plants' tolerance by inhibiting growth. So, how to accurately regulate the activities of miR398 targets and thus make rice better able to adapt to different conditions has great significances in producing rice yields under the current circumstances of shrinking arable lands resulting from global urbanization and increasing salty soil caused by irrigation. Through controlling the expressions of miR398 in different levels, we found down-regulated expression of miR398 targets can promote growth under good growth conditions while up-regulated expressions of the targets can help rice tolerate salt. In this study, we over-expressed miR398 highly, moderately, and lowly, then three concomitantly inverse levels of its targets' expression were obtained. Under normal growth conditions, the transgenic lines with low and moderate levels of over-expressions of miR398 could increase grain yields 14.5% and 7.3%, respectively, although no transgenic lines could survive well under salty conditions simulating real saline-alkali soil. Using short tandem target mimic (STTM) technology to silence miR398 highly, moderately, and lowly respectively, also three inverse levels of its targets' expression were obtained. All three transgenic lines exhibited good agronomic performances under salt stress in inverse to their degrees of STTM, but their growth was inhibited differently under normal conditions. Altogether, we suggest that flexibly manipulating the expression of miR398 is an ideal strategy to help rice survive better and achieve optimized yields under specific conditions.

Identification of Pri-miRNA Stem-Loop Interacting Proteins in Plants Using a Modified Version of the Csy4 CRISPR Endonuclease.

Regulation at the RNA level by RNA-binding proteins (RBPs) and microRNAs (miRNAs) is key to coordinating eukaryotic gene expression. In plants, the importance of miRNAs is highlighted by severe developmental defects in mutants impaired in miRNA biogenesis. MiRNAs are processed from long primary-microRNAs (pri-miRNAs) with internal stem-loop structures by endonucleolytic cleavage. The highly structured stem-loops constitute the basis for the extensive regulation of miRNA biogenesis through interaction with RBPs. However, trans-acting regulators of the biogenesis of specific miRNAs are largely unknown in plants. Therefore, we exploit an RNA-centric approach based on modified versions of the conditional CRISPR nuclease Csy4* to pull down interactors of the Arabidopsis pri-miR398b stem-loop (pri-miR398b-SL) in vitro. We designed three epitope-tagged versions of the inactive Csy4* for the immobilization of the protein together with the pri-miR398b-SL bait on high affinity matrices. After incubation with nucleoplasmic extracts from Arabidopsis and extensive washing, pri-miR398b-SL, along with its specifically bound proteins, were released by re-activating the cleavage activity of the Csy4* upon the addition of imidazole. Co-purified proteins were identified via quantitative mass spectrometry and data sets were compared. In total, we identified more than 400 different proteins, of which 180 are co-purified in at least two out of three independent Csy4*-based RNA pulldowns. Among those, the glycine-rich RNA-binding protein AtRZ-1a was identified in all pulldowns. To analyze the role of AtRZ-1a in miRNA biogenesis, we determined the miR398 expression level in the atrz-1a mutant. Indeed, the absence of AtRZ-1a caused a decrease in the steady-state level of mature miR398 with a concomitant reduction in pri-miR398b levels. Overall, we show that our modified Csy4*-based RNA pulldown strategy is suitable to identify new trans-acting regulators of miRNA biogenesis and provides new insights into the post-transcriptional regulation of miRNA processing by plant RBPs.

Mechanism underlying potato spindle tuber viroid affecting tomato (Solanum lycopersicum): loss of control over reactive oxygen species production

Severe infection of the tomato cultivar ‘Rutgers’ with potato spindle tuber viroid (PSTVd) variants resulted in systemic stunting, leaf malformation, and vein necrosis; accompanied by a rapid increase in reactive oxygen species (ROS) and abnormally high expression of the stress-responsive microRNAs, miR398 and miR398a-3p. The severity of the symptoms, PSTVd accumulation, the high expression of miR398 and miR398a-3p, and the high level of ROS production were positively correlated with the pathogenesis of the PSTVd variants. In contrast, the cytosolic and chloroplast-localized Cu/Zn-superoxide dismutase genes SlSOD4 and SlSOD3, respectively that encode the ROS scavenging enzymes were down-regulated and negatively correlated with the severity of the symptoms. Conversely, in the PSTVd-infected, PSTVd-tolerant (almost asymptomatic) tomato cultivar ‘Moneymaker’ in which PSTVd accumulation was suppressed, the ROS production was as low as in the control, miR398 and miR398a-3p were down-regulated, and almost all the SOD genes were up-regulated. The results indicated that in the PSTVd-sensitive tomato cultivar ‘Rutgers’, infection with the severe PSTVd variant caused suppression of the cytosolic and chloroplast-localized Cu/Zn-SOD genes via PSTVd-induced overexpression of miR398 and miR398a-3, respectively. This condition significantly reduced or eliminated the normal ROS scavenging function and an excess of harmful ROS in cells and tissues seem to have caused severe pathological symptoms accompanied by necrosis.

Identification and function prediction of iron-deficiency-responsive microRNAs in citrus leaves.

The online version contains supplementary material available at 10.1007/s13205-021-02669-z.

ASCORBATE PEROXIDASE6 delays the onset of age-dependent leaf senescence.

Age-dependent changes in reactive oxygen species (ROS) levels are critical in leaf senescence. While H2O2-reducing enzymes such as catalases and cytosolic ASCORBATE PEROXIDASE1 (APX1) tightly control the oxidative load during senescence, their regulation and function are not specific to senescence. Previously, we identified the role of ASCORBATE PEROXIDASE6 (APX6) during seed maturation in Arabidopsis (Arabidopsis thaliana). Here, we show that APX6 is a bona fide senescence-associated gene. APX6 expression is specifically induced in aging leaves and in response to senescence-promoting stimuli such as abscisic acid (ABA), extended darkness, and osmotic stress. apx6 mutants showed early developmental senescence and increased sensitivity to dark stress. Reduced APX activity, increased H2O2 level, and altered redox state of the ascorbate pool in mature pre-senescing green leaves of the apx6 mutants correlated with the early onset of senescence. Using transient expression assays in Nicotiana benthamiana leaves, we unraveled the age-dependent post-transcriptional regulation of APX6. We then identified the coding sequence of APX6 as a potential target of miR398, which is a key regulator of copper redistribution. Furthermore, we showed that mutants of SQUAMOSA PROMOTER BINDING PROTEIN-LIKE7 (SPL7), the master regulator of copper homeostasis and miR398 expression, have a higher APX6 level compared with the wild type, which further increased under copper deficiency. Our study suggests that APX6 is a modulator of ROS/redox homeostasis and signaling in aging leaves that plays an important role in developmental- and stress-induced senescence programs.

Kuraklık Stresi Altındaki Buğday Çeşitlerinde Salisilik Asit Uygulamalarının miRNA İfadesi Üzerine Etkileri

Wheat cultivation in Turkey; is highly affected by environmental factors, such as drought stress, which reduces yields significantly. Applying chemicals that stimulate plant growth is an easy, low-cost, low-risk and effective approach to increase stress tolerance, and salicylic acid is prominent in adapting plants to adverse environmental conditions such as drought stress, salinity, and improving plants' tolerance to stress. In the study, Gün91 was used as drought tolerant variety and Ankara98 was used as the sensitive variety and two different doses (0.1 mM, 0.5mM) of salicylic acid were applied to the plants. Drought stress application was performed one week after salicylic acid application and RNAs were isolated from leaf samples collected from application and control pots, and expression levels of miR156, miR169, miR172, miR319 and mir398 and target genes belonging to these miRNAs were determined. While the expression level of miR156 and miR172 was higher in Day91 with tolerance to drought stress in leaf tissues treated with salicylic acid under drought stress conditions; the level of miR169 was higher in the sensitive Ankara98 variety. In Gün91 variety, miR319 expression level was higher in 0.5 mM salicylic acid + drought application, whereas in Ankara98 variety was higher in 0.1 mM salicylic acid + drought application. The miR398 expression level showed a significant decrease in both Gün91 and Ankara98 varieties in the plant groups where salicylic acid and drought stress were applied together compared to the control group. As a result; with this study, it was emphasized that salicylic acid is an important signal molecule in response to stress and it mitigates the effect in stress conditions, and the tolerance mechanism of drought tolerant and sensitive varieties with salicylic acid application were different.

SPL7 locally regulates copper-homeostasis-related genes in Arabidopsis

In Arabidopsis, a central regulator of copper (Cu) homeostasis is the transcription factor SQUAMOSA promoter binding protein-like7 (SPL7). Under Cu deficiency, SPL7 induces the expression of miR398, which suppresses the expression of the genes CSD1 and CSD2, which encode cytosolic and chloroplastic isoforms of Cu/Zn superoxide dismutase, respectively. Consequently, the limited Cu is preferentially assigned to plastocyanin, which is essential for photosynthetic electron transport. Consistent with this function of miR398 related to photosynthesis, its expression is strongly induced in leaves. In this study, however, we showed that SPL7 was transcribed mainly around the vasculature in roots, where Cu levels were likely sensed. To test the possible long-distance signaling of Cu availability from roots to shoots, we conducted a series of grafting experiments using spl7 mutant and wild-type (WT) plants. Expression of Cu-responsive microRNAs and the resulting suppression of CSD1 and CSD2 mRNAs were observed in leaves only when the aerial part was from WT plants, in which a low level of SPL7 was transcribed also in the vascular tissues. Although local sensing of Cu was disturbed in the spl7 mutant, the Cu level was not affected in the shoots. SPL7 is expressed in specific cell layers in both roots and shoots and locally senses Cu availability, transmitting the information to surrounding cells.

Indicators of environmental contamination by heavy metals in leaves of Taraxacum officinale in two zones of the metropolitan area of Mexico City.

The present study was designed to detect the effect of heavy metals in two zones of the Metropolitan Area of Mexico City (MAMC), the Centro de Ciencias de la Atmósfera (CCA), and the Altzomoni station in the Iztaccíhuatl-Popocatépetl National Park. Taraxacum officinale was selected as the indicator organism of responses to atmospheric contamination by heavy metals. Determinations of heavy metals were performed, and total mRNA was extracted to quantify the expression of microRNA398 (miR398), superoxide dismutase 2 (CSD2), and the amounts of free radicals using the bromide of 3-(4,5-dimethylthiazole-2-ilo)-2,5-diphenyltetrazole (MTT) salts reduction assay. Results from the Altzomoni station showed high concentrations of five heavy metals, especially Aluminum, while three heavy metals were identified in the CCA-UNAM zone, most importantly, Vanadium, both in the dry season; miR398 expression presented subtle changes but was greater in the leaves from the stations with higher concentrations of heavy metals. Observations included a significant expression of CSD2, mainly in the dry season in both study zones, where levels were significant with respect to controls (p < 0.05). Reduced MTT was also higher in the dry season than in the rainy season (p < 0.05). In conclusion, the increase in heavy metals on the leaves of Taraxacum officinale induces increased expression of the CSD2 gene and reduced MTT; thus, they can be used as indicators for biomonitoring heavy metal concentrations.

MiR398 and miR395 are involved in response to SO2 stress in Arabidopsis thaliana.

Sulfur dioxide (SO2) is a common air pollutant that has adverse effects on plants. MicroRNAs (miRNAs) are small noncoding RNA that play critical roles in plant development and stress response. In this study, we found that two miRNAs, miR398 and miR395, were differentially expressed in Arabidopsis shoots under SO2 stress. The expression of miR398 was down-regulated, and the transcript levels of its target genes, Cu/Zn superoxide dismutases (CSD1 and CSD2), were increased during SO2 exposure. The activity of superoxide dismutase (SOD), one of the major antioxidant enzymes, was enhanced with the increase in the CSD transcript level, suggesting an important role of miR398 in response to SO2-induced oxidative stress. Meanwhile, the expression of miR395 was increased, and the transcript levels of its target genes, ATP sulfurylases (APS3 and APS4) and a low-affinity sulfate transporter (SULTR2;1), were decreased in Arabidopsis shoots, showing that miR395 played important roles in the regulation of sulfate assimilation and translocation during SO2 exposure. The content of glutathione (GSH), an important sulfur-containing antioxidant, was enhanced with the changes in sulfur metabolism in Arabidopsis shoots under SO2 stress. These results showed that both miR398 and miR395 were involved in protecting plants from oxidative damage during SO2 exposure. Many stress-responsive cis-elements were found in the promoter regions of MIR398 and MIR395, suggesting that these miRNAs might respond to various environmental conditions, including SO2 stress. Overall, our study provides an insight into the regulatory roles of miRNAs in response to SO2 stress in plants, and highlights the molecular mechanisms of plant adaptation to environmental stress.

A removable virus vector suitable for plant genome editing.

Plant genome editing is achieved by the expression of sequence-specific nucleases (SSNs). RNA virus vector-mediated expression of SSNs is a promising approach for transgene integration-free targeted mutagenesis in plants. However, the removal of virus vectors from infected plants is challenging because no antiviral drugs are available against plant viruses. Here, we developed a removable RNA virus vector that carries the target site of tobacco microRNA398 (miR398) whose expression is induced during shoot regeneration. In the inoculated leaves in which expression of miR398 is not induced, insertion of the miR398 target site did not affect the practicability of the virus vector. When shoots were regenerated from the infected leaves, miR398 was expressed and viral RNA was eliminated. The virus vector successfully expressed SSNs in inoculated leaves, from which virus-free genome-edited plants were regenerated via tissue culture.

Excess boron responsive regulations of antioxidative mechanism at physio-biochemical and molecular levels in Arabidopsis thaliana

This work was aimed to evaluate the effect of boron (B) toxicity on oxidative damage level, non-enzymatic antioxidant accumulation such as anthocyanin, flavonoid and proline and expression levels of antioxidant enzymes including superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT) and glutathione reductase (GR) and their respective activities as well as expression levels of miR398 and miR408 in Arabidopsis thaliana. Plants were germinated and grown on MS medium containing 1 mM B (1B) and 3 mM B (3B) for 14 d. Toxic B led to a decrease of photosynthetic pigments and an increase in accumulation of total soluble and insoluble sugars in accordance with phenotypically viewed chlorosis of seedlings through increasing level of B concentration. Along with these inhibitions, a corresponding increase in contents of flavonoid, anthocyanin and proline occurred that provoked oxidative stress tolerance. 3B caused a remarkable increase in total SOD activity whereas the activities of APX, GR and CAT remained unchanged as verified by expected increase in H2O2 content. In contrast to GR, the coincidence was found between the expressions of SOD and APX genes and their respective activities. 1B induced mir398 expression, whereas 3B did not cause any significant change in expression of mir408 and mir398. Expression levels of GR genes were coordinately regulated with DHAR2 expression. Moreover, the changes in expression level of MDAR2 was in accordance with changes in APX6 expression and total APX activity, indicating fine-tuned regulation of ascorbate-glutathione cycle which might trigger antioxidative responses against B toxicity in Arabidopsis thaliana.

Establishment and in-house validation of stem-loop RT PCR method for MicroRNA398 expression analysis

MicroRNAs (miRNAs) belong to the class of small non-coding RNAs which have important roles throughout development as well as in plant response to diverse environmental stresses. Some of plant miRNAs are essential for regulation and maintenance of nutritive homeostasis when nutrients are in excess or shortage comparing to optimal concentration for certain plant species. Better understanding of miRNAs functions implies development of efficient technology for profiling their gene expression. We set out to establish validate the methodology for miRNA gene expression analysis in cucumber grown under suboptimal mineral nutrient regimes, including iron deficiency. Reverse transcription by ?stem-loop? primers in combination with Real time PCR method is one of potential approaches for quantification of miRNA gene expression. In this paper we presented a method for ?stem loop? primer design specific for miR398, as well as reaction optimization and determination of Real time PCR efficiency. Proving the accuracy of this method was imperative as ?stem loop? RT which consider separate transcription of target and endogenous control. The method was verified by comparison of the obtained data with results of miR398 expression achieved using a commercial kit based on simultaneous conversion of all RNAs in cDNAs.

Spatial‐temporal analysis of zinc homeostasis reveals the response mechanisms to acute zinc deficiency in Sorghum bicolor

Zinc (Zn) is an essential micronutrient in plants. The activity of copper/zinc superoxide dismutase (CSD) and carbonic anhydrase (CA) correlate with differences in Zn efficiency in plants; therefore, it is reasonable to hypothesize the existence of a Zn economy model that saves Zn for these essential Zn proteins during Zn deficiency. However, up to this point, direct evidence for the idea that CSD and/or CA might be priorities for Zn delivery has been lacking. Here, we investigated the spatial-temporal effects of acute Zn depletion and resupply by integrating physiological studies and molecular analyses using hydroponically grown Sorghum. The elevated expression of miR398 repressed CSD expression in roots, whereas the reduced expression of miR528 resulted in a relatively stable level of CSD expression in Sorghum leaves under Zn depletion. Spatial-temporal analysis after Zn resupply to previously depleted plants revealed that the expression and activity of CA were the first to recover after Zn addition, whereas the recovery of the activities of CSD and alcohol dehydrogenase (ADH) was delayed, suggesting that CA receives priority in Zn delivery over CSD and ADH. Our results also indicate that microRNAs (miRNAs) are important regulators of the response of Zn deficiency in plants.

Identification of sucrose-responsive microRNAs reveals sucrose-regulated copper accumulations in an SPL7-dependent and independent manner in Arabidopsis thaliana

Sucrose induces the expression of miR398 and the production of miR398 is controlled by SQUAMOSA promoter binding protein-like7 (SPL7) transcription factor under copper deficiency in Arabidopsis thaliana. Little else, however, is known about the sucrose-regulated copper homeostasis in Arabidopsis. Here, we employed the microarray technology to screen for sucrose-responsive microRNAs (miRNAs), and identified several candidates using northern blotting. In addition to miR398, miR408, miR319, and miR160 are also responsive to sucrose. Furthermore, the induction of miR398 and miR408 by sucrose depends on the presence of SPL7. MiR398 and miR408 induction by high sucrose was eliminated by high copper. Meanwhile, high sucrose treatment strongly suppressed copper accumulation. Knock-down of SPL7 dramatically reduced copper accumulation in plants under low sucrose, but this effect was compromised in the presence of high levels of sucrose. Taken together, these results suggest a connection between sucrose signaling and copper accumulation in cells, and that sucrose-regulated copper accumulation is both SPL7-dependent and SPL7-independent in Arabidopsis.

Plants contain two SCO proteins that are differentially involved in cytochrome c oxidase function and copper and redox homeostasis

Two Arabidopsis thaliana genes (HCC1 and HCC2), resulting from a duplication that took place before the emergence of flowering plants, encode proteins with homology to the SCO proteins involved in copper insertion during cytochrome c oxidase (COX) assembly in other organisms. Heterozygote HCC1 mutant plants produce 25% abnormal seeds with defective embryos arrested at the heart or torpedo stage. These embryos lack COX activity, suggesting that the requirement of HCC1 during the early stages of plant development is related with its COX assembly function. Homozygote HCC2 mutant plants develop normally and do not show changes in COX2 levels. These plants display increased sensitivity of root growth to increased copper and a higher expression of miR398 and other genes that respond to copper limitation, in spite of the fact that they have a higher copper content than the wild type. HCC2 mutant plants also show increased expression of stress-responsive genes. The results suggest that HCC1 is the protein involved in COX biogenesis and that HCC2, that lacks the cysteines and histidine putatively involved in copper binding, functions in copper sensing and redox homeostasis. In addition, plants that overexpress HCC1 have an altered response of root elongation to changes in copper in the growth medium and increased expression of two low-copper-responsive genes, suggesting that HCC1 may also have a role in copper homeostasis.

MIR398 and expression regulation of the cytoplasmic Cu/Zn-superoxide dismutase gene in Thellungiella halophila plants under stress conditions

In the salt-tolerant plant Thellungiella halophila, expression of microRNA from MIR398 family, which regulated expression of superoxide dismutase (Cu/Zn-SOD) in Arabidopsis thaliana at posttranscriptional level, was revealed. The effects of various salinity levels, illumination intensity, and UV-B radiation on MIR398 expression was demonstrated by Northern-blot hybridization. These stressors changed the level of MIR398 expression in roots and leaves in opposite directions, which indicates a possible stress-dependent transport of MIR398 over the plant. Under salinity stress and UV-B irradiation, a negative correlation was observed between expression of MIR398 and its target, mRNA of Cu/Zn-SOD, one of the key enzymes of plant antioxidant defense. Thus, MIR398-dependent expression of CSD1 gene is characteristic of not only glycophytes but also halophytes, being organ-unspecific and independent of abiotic stressors affecting the plant.

Biotic and abiotic stress down-regulate miR398 expression in Arabidopsis

MicroRNA398 targets two Cu/Zn superoxide dismutases (CSD1 and CSD2) in higher plants. Previous investigations revealed both decreased miR398 expression during high Cu(2+) or paraquat stress and increased expression under low Cu(2+) or high sucrose in the growth medium. Here, we show that additional abiotic stresses such as ozone and salinity also affect miR398 levels. Ozone fumigation decreased miR398 levels that were gradually restored to normal levels after relieved from the stress. Furthermore, miR398 levels decreased in Arabidopsis leaves infiltrated with avirulent strains of Pseudomonas syringae pv. tomato, Pst DC3000 (avrRpm1 or avrRpt2) but not the virulent strain Pst DC3000. To our knowledge, miR398 is the first miRNA shown to be down-regulated in response to biotic stress (P. syringae). CSD1, but not CSD2, mRNA levels were negatively correlated with miR398 levels during ozone, salinity and biotic stress, suggesting that CSD2 regulation is not strictly under miR398 control during diverse stresses. Overall, this study further establishes a link between oxidative stress and miR398 in Arabidopsis.

Posttranscriptional Induction of Two Cu/Zn Superoxide Dismutase Genes in Arabidopsis Is Mediated by Downregulation of miR398 and Important for Oxidative Stress Tolerance

MicroRNAs (miRNAs) are a class of regulatory RNAs of approximately 21 nucleotides that posttranscriptionally regulate gene expression by directing mRNA cleavage or translational inhibition. Increasing evidence points to a potential role of miRNAs in diverse physiological processes. miR398 targets two closely related Cu/Zn superoxide dismutases (cytosolic CSD1 and chloroplastic CSD2) that can detoxify superoxide radicals. CSD1 and CSD2 transcripts are induced in response to oxidative stress, but the regulatory mechanism of the induction is unknown. Here, we show that miR398 expression is downregulated transcriptionally by oxidative stresses, and this downregulation is important for posttranscriptional CSD1 and CSD2 mRNA accumulation and oxidative stress tolerance. We also provide evidence for an important role of miR398 in specifying the spatial and temporal expression patterns of CSD1 and CSD2 mRNAs. Our results suggest that CSD1 and CSD2 expression is fine-tuned by miR398-directed mRNA cleavage. Additionally, we show that transgenic Arabidopsis thaliana plants overexpressing a miR398-resistant form of CSD2 accumulate more CSD2 mRNA than plants overexpressing a regular CSD2 and are consequently much more tolerant to high light, heavy metals, and other oxidative stresses. Thus, relieving miR398-guided suppression of CSD2 in transgenic plants is an effective new approach to improving plant productivity under oxidative stress conditions.