Transcriptomic and physiological effects of polyethylene microplastics on Zea mays seedlings and their role as a vector for organic pollutants.

The widespread employment of plastics in recent decades has resulted in the accumulation of plastic residues in all ecosystems. Their presence and degradation into small particles such as microplastics (MPs) may have a negative effect on plant development and therefore on crop production. In this study, the effects of two types of polyethylene MPs on Zea mays seedlings cultured in vitro were analysed. In addition, four organic pollutants (ibuprofen, simazine, sertraline, and amoxicillin) were adsorbed by the MPs to evaluate their capacity as other contaminant vectors. The development of the plants was negatively affected by MPs alone or with the organic compounds. The strongest effect was observed in the W-MPs treatments, with a reduction in leaf and root length near 70%. Chlorophyll content was also differentially affected depending on the treatment. Transcriptome analysis showed that MPs affected gene expression in the roots of maize seedlings. As observed in the physiological parameters analysed, some gene expression changes were associated with specific treatments, such as changes in sugar transport genes in the B-MIX treatment. These results contribute to a better understanding of the molecular mechanisms of plants in regard to plastic stress responses.

Seed Longevity and Ageing: A Review on Physiological and Genetic Factors with an Emphasis on Hormonal Regulation.

Upon storage, seeds inevitably age and lose their viability over time, which determines their longevity. Longevity correlates with successful seed germination and enhancing this trait is of fundamental importance for long-term seed storage (germplasm conservation) and crop improvement. Seed longevity is governed by a complex interplay between genetic factors and environmental conditions experienced during seed development and after-ripening that will shape seed physiology. Several factors have been associated with seed ageing such as oxidative stress responses, DNA repair enzymes, and composition of seed layers. Phytohormones, mainly abscisic acid, auxins, and gibberellins, have also emerged as prominent endogenous regulators of seed longevity, and their study has provided new regulators of longevity. Gaining a thorough understanding of how hormonal signalling genes and pathways are integrated with downstream mechanisms related to seed longevity is essential for formulating strategies aimed at preserving seed quality and viability. A relevant aspect related to research in seed longevity is the existence of significant differences between results depending on the seed equilibrium relative humidity conditions used to study seed ageing. Hence, this review delves into the genetic, environmental and experimental factors affecting seed ageing and longevity, with a particular focus on their hormonal regulation. We also provide gene network models underlying hormone signalling aimed to help visualize their integration into seed longevity and ageing. We believe that the format used to present the information bolsters its value as a resource to support seed longevity research for seed conservation and crop improvement.

Application of the MSAP Technique to Evaluate Epigenetic Changes in Plant Conservation.

Epigenetic variation, and particularly DNA methylation, is involved in plasticity and responses to changes in the environment. Conservation biology studies have focused on the measurement of this variation to establish demographic parameters, diversity levels and population structure to design the appropriate conservation strategies. However, in ex situ conservation approaches, the main objective is to guarantee the characteristics of the conserved material (phenotype and epi-genetic). We review the use of the Methylation Sensitive Amplified Polymorphism (MSAP) technique to detect changes in the DNA methylation patterns of plant material conserved by the main ex situ plant conservation methods: seed banks, in vitro slow growth and cryopreservation. Comparison of DNA methylation patterns before and after conservation is a useful tool to check the fidelity of the regenerated plants, and, at the same time, may be related with other genetic variations that might appear during the conservation process (i.e., somaclonal variation). Analyses of MSAP profiles can be useful in the management of ex situ plant conservation but differs in the approach used in the in situ conservation. Likewise, an easy-to-use methodology is necessary for a rapid interpretation of data, in order to be readily implemented by conservation managers.

Genetic and Epigenetic Stability in Rye Seeds under Different Storage Conditions: Ageing and Oxygen Effect.

Seed ageing is a complex process and can be described as the loss of viability or quality with time. It is important to elucidate whether genetic and epigenetic stability is altered in stored seeds and in seedlings produced from them. Non-stored and stored rye seeds at different stages of ageing were compared, as well as the seedlings obtained from them. Seeds were stored at 35 °C and 15% water content, under vacuum or air atmosphere. DNA of seeds and seedlings was isolated at three stages of the deterioration curve: P75 (13 days), P20 (29 days), and P0 (36 days). Genetic stability was assessed by RAPD technique, and epigenetic changes by MSAP markers. While seeds showed genetic stability after storage, the similarity of seedlings obtained from seeds stored for 29 days was lower (95%) when compared to seedlings from control seeds. Epigenetic changes were between 15% and 30% (both de novo methylation and demethylation) in the stored seeds compared to control seeds, with no differences between 13 and 29 days of storage with either air or vacuum atmospheres. In seedlings, epigenetic changes significantly increased with storage time. In conclusion, ageing increased epigenetic instability in both seeds and seedlings, when compared to controls.