RESUMEN
Cadmium (Cd) is a heavy metal that is widely contaminating the environment due to its uses in industries as corrosive reagents, paints, batteries, etc. Cd can easily be absorbed through plant roots and may have serious negative impacts on plant growth. To investigate the mechanisms utilized by plants to cope with Cd toxicity, an experiment was conducted on maize seedlings. We observed that the plant growth and photosynthetic mechanism were negatively influenced during 20 days of Cd stress. The expression levels of ornithine decarboxylase (ORDC) increased in the six seedlings under Cd exposure compared to the control. However, Cd toxicity led to an increase in putrescine (Put) content only on day 15 when compared to the control plants. In fact, with the exception of day 15, the increases in the ORDC transcript levels did not show a direct correlation with the observed increases in Put content. Spermidine and Spermine levels were reduced on day 6 by Cd application, which was parallel with suppressed Spermidine synthase gene. However, an increase in Spermidine and Spermine levels was observed on day 12 along with a significant elevation in Spermidine synthase expression. On day 6, Cd was observed to start accumulating in the root with an increase in the expression of microRNA 528; while on day 15, Cd started to be observed in the shoot part with an increase in microRNA 390 and microRNA 168. These results imply that different miRNAs may regulate polyamines (PAs) in maize under Cd toxicity, suggesting a plant-derived strategy to commit a PAs/miRNA-regulated mechanism/s in different developmental stages (time points) in response to Cd exposure.
RESUMEN
Background: Mentha piperita L. is one of the most important aromatic crops and is cultivated worldwide for essential oils (EOs). Objectives: The aim of the present study was to investigate the potential of two cyanobacteria, Anabaena vaginicola ISB42 and Nostoc spongiaeforme var. tenue ISB65, as biological-elicitors to improve the growth and essential oil production of M. piperita. Materials and Methods: In this experiment, inoculation of M. piperita with cyanobacteria was performed by adding 1% cyanobacterial suspension to the soil of treated pots on the first time of planting and every 20 days thereafter. The experiment was performed in a randomized complete block design in an experimental greenhouse condition. After 90 days planting, the vegetative growth factors, the content of photosynthetic pigments, as well as the quantity and quality of EOs of treated and control plants were evaluated. Also, quantitative changes in the expression of some menthol biosynthesis-related genes were investigated. Results: Cyanobacterial application led to significant increases in M. piperita growth indices including root and shoot biomass, leaf number, leaf area, node number and ramification, as well as photosynthetic pigments content. The statistical analysis showed a 41-75 % increase in some of these growth indices, especially in Nostoc-treated plants. A. vaginicola and N. spongiaeforme var. tenue inoculation led to a 13% and 25% increase in the EOs content of M. piperita, respectively. The EOs components were also affected by cyanobacterial treatments. According to the statistical analysis, Nostoc-treated plants showed the highest amount of (-)-menthone and (-)-limonene, with a 2.36 and 1.87-fold increase compared to the control. A. vaginicola and N. spongiaeforme var. tenue inoculation also led to 40% and 98% increase in transcript level of (-)-limonene synthase gene, respectively. The expression of the (-)-menthone reductase gene, was also increased by 65% and 55% in response to A. vaginicola and N. spongiaeforme var. tenue application, respectively. Conclusions: Our data demonstrated that in addition to growth enhancement, these two heterocystous cyanobacteria improved the quantity and quality of EOs by up-regulating the key genes involved in the menthol biosynthetic pathway. Based on our results, these cyanobacteria can be considered valuable candidates in the formulation of low-cost and environmentally friendly biofertilizers in sustainable peppermint production.
RESUMEN
Rapid and complete seed germination results in the rapid initial growth of plants. In this study, aqueous extracts (boiling, maceration + filtration, and maceration + autoclave) of Ganoderma lucidum and Pleurotus eryngii were used to improve seed germination of three crops (maize, clover, and alfalfa). The results revealed that boiled water extractions of G. lucidum positively affected seed germination of clover and alfalfa. Moreover, P. eryngii boiling extract could increase the vigor index II in alfalfa. The results achieved are comparable with those gained by phytohormones and in some cases were even better. From these findings, it can be concluded that the existing metabolites in aqueous extracts of G. lucidum and P. eryngii can be used to enhance seed germination effectively and even increase the leaf area of crop plants.
Asunto(s)
Agaricales , Pleurotus , Reishi , Germinación , Plantones , Semillas , AguaRESUMEN
Although full sequence data of several embryogenesis-related genes are available in conifers, their functions are still poorly understood. In this study, we focused on the transcription factor WUSCHEL-related HOMEOBOX 2 (WOX2), which is involved in determination of the apical domain during early embryogenesis, and is required for initiation of the stem cell program in the embryogenic shoot meristem of Arabidopsis. We studied the effects of constitutive overexpression of Pinus pinaster WOX2 (PpWOX2) by Agrobacterium-mediated transformation of P. pinaster somatic embryos and Arabidopsis seedlings. Overexpression of PpWOX2 during proliferation and maturation of somatic embryos of P. pinaster led to alterations in the quantity and quality of cotyledonary embryos. In addition, transgenic somatic seedlings of P. pinaster showed non-embryogenic callus formation in the region of roots and subsequently inhibited root growth. Overexpression of PpWOX2 in Arabidopsis promoted somatic embryogenesis and organogenesis in a part of the transgenic seedlings of the first and second generations. A concomitant increased expression of endogenous embryogenesis-related genes such as AtLEC1 was detected in transgenic plants of the first generation. Various plant phenotypes observed from single overexpressing transgenic lines of the second generation suggest some significant interactions between PpWOX2 and AtWOX2. As an explanation, functional redundancy in the WOX family is suggested for seed plants. Our results demonstrate that the constitutive high expression of PpWOX2 in Arabidopsis and P. pinaster affected embryogenesis-related traits. These findings further support some evolutionary conserved roles of this gene in embryo development of seed plants and have practical implications toward somatic embryogenesis induction in conifers.
RESUMEN
The aim of this study was to contrast the effects of drought stress on polyamine oxidases gene expression and activity as well as photosynthetic efficiency in relatively tolerant (Karoon) and sensitive (260) maize genotype. d Reduction in leaf relative water content as a result of drought led to increase in root growth, but diminished shoot growth indices. Under drought stress, activity of antioxidant enzyme, catalase, significantly increased in both genotypes, whereas significant higher activity of superoxide dismutase and peroxidase was only observed in Karoon genotype. Expression of polyamine oxidase (PAO) genes (zmPAO1, zmPAO2, zmPAO3, zmPAO4, zmPAO5, zmPAO6) and activity of enzymatic polyamine oxidation was increased in both genotypes under drought stress. The enhancement in PAO gene expression and enzyme activity was more prominent in Karoon cultivar compared to 260. Chlorophyll a fluorescence and fast induction kinetics were negatively influenced by drought stress. These parameters were more affected in 260 cultivar compared with Karoon. Our results suggest that under drought stress, higher activity of polyamine oxidase pathway in backconversion of Spermine and spermidine to putrescine (protectant of photosynthetic apparatus) as well as higher antioxidant enzymes activity in Karoon cultivar, may play a role in higher efficiency of photosynthetic process in this cultivar.
