RESUMEN
Physiological and molecular marker-based changes were studied in the tissues of two-year-old Pyrus pyraster (L.) Burgsd. seedlings under salt treatment. For 60 days, 5 mL of 100 mM NaCl solution was applied to each plant per day to a cumulative volume of 300 mL in the substrate. In response to osmotic stress, the seedlings increased their water use efficiency (WUE) on day 20 of regular NaCl application and maintained a stable net photosynthetic rate (An) per unit area. Under conditions of increasing salinity, the young plants maintained a balanced water regime of the leaf tissues (Ψwl). The seedlings invested mass to their root growth (R/S), retained a substantial portion (72%) of Na+ ions in the roots, and protected their leaves against intoxication and damage. A significant decrease in the leaf gas exchange parameters (gs, E, An) was manifested on day 60 of the experiment when the cumulative NaCl intake was 300 mL per plant. The variability in the reactions of the seedlings to salinity is related to the use of open-pollinated progeny (54 genotypes) in the experiment. Lus-miR168 showed tissue- and genotype-specific genome responses to the applied stress. Polymorphic miRNA-based loci were mostly detected in the root samples on the 20th and 35th days of the experiment. The cumulative effect of the salt treatment was reflected in the predominance of polymorphic loci in the leaves. We can confirm that miRNA-based markers represent a sensitive detection tool for plant stress response on an individual level. The screening and selection of the optimal type of miRNA for this type of research is crucial. The cytochrome P450-Based Analog (PBA) techniques were unable to detect polymorphism among the control and treated seedlings, except for the primer pair CYP2BF+R, where, in the roots of the stressed plant, insertions in the amplicons were obtained. The expression ratios of cytochrome P450 in the salt-stressed plants were higher in the roots in the case of 20/100 mL and in the leaves with higher doses. The observed physiological and molecular responses to salinity reflect the potential of P. pyraster seedlings in adaptation to osmotic and ionic stress.
RESUMEN
Lignans, as secondary metabolites synthesized within a phenylpropanoid pathway, play various roles in plants, including their involvement in growth and plant defense processes. The health and nutritional benefits of lignans are unquestionable, and many studies have been devoted to these attributes. Although the regulatory role of miRNAs in the biosynthesis of secondary metabolites has been widely reported, there is no systematic review available on the miRNA-based regulatory mechanism of lignans biosynthesis. However, the genetic background of lignan biosynthesis in plants is well characterized. We attempted to put together a regulatory mosaic based on current knowledge describing miRNA-mediated regulation of genes, enzymes, or transcription factors involved in this biosynthesis process. At the same time, we would like to underline the fact that further research is necessary to improve our understanding of the miRNAs regulating plant lignan biosynthesis by exploitation of current approaches for functional identification of miRNAs.
