Low Long Terminal Repeat (LTR)-Retrotransposon Expression in Leaves of the Marine Phanerogam Posidonia Oceanica L.

Abstract

Seagrasses as Posidonia oceanica reproduce mostly by vegetative propagation, which can reduce genetic variability within populations. Since, in clonally propagated species, insurgence of genetic variability can be determined by the activity of transposable elements, we have estimated the activity of such repeat elements by measuring their expression level in the leaves of plants from a Mediterranean site, for which Illumina complementary DNA (cDNA) sequence reads (produced from RNAs isolated by leaves of plants from deep and shallow meadows) were publicly available. Firstly, we produced a collection of retrotransposon-related sequences and then mapped Illumina cDNA reads onto these sequences. With this approach, it was evident that Posidonia retrotransposons are, in general, barely expressed; only nine elements resulted transcribed at levels comparable with those of reference genes encoding tubulins and actins. Differences in transcript abundance were observed according to the superfamily and the lineage to which the retrotransposons belonged. Only small differences were observed between retrotransposon expression levels in leaves of shallow and deep Posidonia meadow stands, whereas one TAR/Tork element resulted differentially expressed in deep plants exposed to heat. It can be concluded that, in P. oceanica, the contribution of retrotransposon activity to genetic variability is reduced, although the nine specific active elements could actually produce new structural variations.

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“…tricocharpa, 21 LTR-REs belonging both to Copia and Gypsy superfamilies, were overexpressed in leaf after short and prolonged exposure to drought, cold, heat, and salt stresses, whereas 60 TEs showed a specific down regulation after that same abiotic stimuli occurred . Similarly, overregulation of a RE, subsequent to deep shallow heat exposure, was observed in P. oceanica (Vangelisti et al, 2020).…”

“…The source of the photos of this figure is the site https://www.pianteinsolite.it/ stimuli, showing a significant overexpression after abcisic acid treatment . Other examples of TE regulation by abiotic stresses were observed in Poplar (Populus trichocarpa) and in the marine phenerogam Posidonia oceanica (Vangelisti et al, 2020;. In P.…”

“…In fact, HaCRE1 is usually constitutively expressed both in leaf and root, and in addition can be regulated by mimicking abiotic stimuli, showing a significant overexpression after abcisic acid treatment (Vangelisti, Mascagni, Giordani, et al, 2019). Other examples of TE regulation by abiotic stresses were observed in Poplar ( Populus trichocarpa ) and in the marine phenerogam Posidonia oceanica (Vangelisti et al, 2020; Vangelisti, Mascagni, Usai, et al, 2019). In P .…”

“…Generally, the mobilization of a TE occurs when the organism is subject to conditions of genomic stress such as biotic or abiotic stresses, polyploidy and interspecific hybridizations typical in plants but not completely absent in animals (Bourque et al, 2018; Casacuberta & González, 2013; Dubin, Mittelsten Scheid, & Becker, 2018; Mascagni et al, 2020; Usai et al, 2020; Vangelisti, Mascagni, Giordani, et al, 2019; Vangelisti, Mascagni, Usai, et al, 2019; Vangelisti, Usai, et al, 2019, 2020; Zhao et al, 2018). Given also the irregularity in the course of evolution, with periods of rapid change alternated to long periods of stability, it is likely that in some cases the TEs have expanded within the genomes as predicted by the theory of punctuated equilibria (Eldredge & Gould, 1972).…”

“…Similarly, overregulation of a RE, subsequent to deep shallow heat exposure, was observed in P . oceanica (Vangelisti et al, 2020).…”