Abstract:SummarySeveral clades of mangrove trees independently invade the interface between land and sea at the margin of woody plant distribution. As phenotypic convergence among mangroves is common, the possibility of convergent adaptation in their genomes is quite intriguing.To study this molecular convergence, we sequenced multiple mangrove genomes. In this study, we focused on the evolution of transposable elements (TEs) in relation to the genome size evolution. TEs, generally considered genomic parasites, are the… Show more
“…To my knowledge, Lyu et al . 's study is the first to demonstrate that independent but parallel adaptive events (specialization to the intertidal habitat) affect convergent shifts in GS and composition across species.…”
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confidence: 89%
“…However, few examples have made this link, and even fewer have been able to identify the specific genomic components that contribute to GS changes. In this issue of New Phytologist , Lyu et al . (pp. 428–438) do both by focusing on genome evolution in mangroves. ‘The mangrove study is unique in demonstrating parallel shifts in GS across different species.’ …”
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confidence: 99%
“…Lyu et al . asked whether adaptation to the mangrove habitat has had a consistent effect on GS. To answer this question, they compared GS estimates among three groups: 12 true mangroves, seven mangrove‐associated species and a set of non‐mangrove species from 58 plant families.…”
mentioning
confidence: 99%
“…This fact implies that mangroves have smaller genomes because they have fewer TEs. To test this idea, Lyu et al . gathered whole‐genome sequence data from four mangrove species, representing at least three independent mangrove origins, and 29 closely‐related species. They then annotated TEs within each of the 33 genomes.…”
mentioning
confidence: 99%
“…There are two non‐exclusive possibilities as to how mangrove genomes have become small: either TEs were deleted rapidly from genomes or TEs had low birth rates. To contrast TE death and birth rates, Lyu et al . analyzed long terminal repeat retrotransposons (LTR‐RTs). They found that mangroves were unique among their sample of species, because they lacked evidence for recent LTR‐RT insertion events.…”
“…To my knowledge, Lyu et al . 's study is the first to demonstrate that independent but parallel adaptive events (specialization to the intertidal habitat) affect convergent shifts in GS and composition across species.…”
mentioning
confidence: 89%
“…However, few examples have made this link, and even fewer have been able to identify the specific genomic components that contribute to GS changes. In this issue of New Phytologist , Lyu et al . (pp. 428–438) do both by focusing on genome evolution in mangroves. ‘The mangrove study is unique in demonstrating parallel shifts in GS across different species.’ …”
mentioning
confidence: 99%
“…Lyu et al . asked whether adaptation to the mangrove habitat has had a consistent effect on GS. To answer this question, they compared GS estimates among three groups: 12 true mangroves, seven mangrove‐associated species and a set of non‐mangrove species from 58 plant families.…”
mentioning
confidence: 99%
“…This fact implies that mangroves have smaller genomes because they have fewer TEs. To test this idea, Lyu et al . gathered whole‐genome sequence data from four mangrove species, representing at least three independent mangrove origins, and 29 closely‐related species. They then annotated TEs within each of the 33 genomes.…”
mentioning
confidence: 99%
“…There are two non‐exclusive possibilities as to how mangrove genomes have become small: either TEs were deleted rapidly from genomes or TEs had low birth rates. To contrast TE death and birth rates, Lyu et al . analyzed long terminal repeat retrotransposons (LTR‐RTs). They found that mangroves were unique among their sample of species, because they lacked evidence for recent LTR‐RT insertion events.…”
Citation: Meyerson, L. A., P. Py sek, M. Lu canov a, S. Wigginton, C.-T. Tran, and J. T. Cronin. 2020. Plant genome size influences stress tolerance of invasive and native plants via plasticity. Ecosphere 11(5):Abstract. Plant genome size influences the functional relationships between cellular and whole-plant physiology, but we know little about its importance to plant tolerance of environmental stressors and how it contributes to range limits and invasion success. We used native and invasive lineages of a wetland plant to provide the first experimental test of the Large Genome Constraint Hypothesis (LGCH)-that plants with large genomes are less tolerant of environmental stress and less plastic under stress gradients than plants with small genomes. We predicted that populations with larger genomes would have a lower tolerance and less plasticity to a stress gradient than populations with smaller genomes. In replicated experiments in northern and southern climates in the United States, we subjected plants from 35 populations varying in genome size and lineage to two salinity treatments. We measured traits associated with growth, physiology, nutrition, defense, and plasticity. Using AICc model selection, we found all plant traits, except stomatal conductance, were influenced by environmental stressors and genome size. Increasing salinity was stressful to plants and affected most plant traits. Notably, biomass in the high-salinity treatment was 3.0 and 4.9 times lower for the invasive and native lineages, respectively. Plants in the warmer southern greenhouse had higher biomass, stomate density, stomatal conductance, leaf toughness, and lower aboveground percentage of N and total phenolics than in the northern greenhouse. Moreover, responses to the salinity gradient were generally much stronger in the southern than northern greenhouse. Aboveground biomass increased significantly with genome size for the invasive lineage (43% across genome sizes) but not for the native. For 8 of 20 lineage trait comparisons, greenhouse location 9 genome size interaction was also significant. Interestingly, the slope of the relationship between genome size and trait means was in the opposite direction for some traits between the gardens providing mixed support for LGCH. Finally, for 30% of the comparisons, plasticity was significantly related to genome size-for some plant traits, the relationship was positive, and in others, it was negative. Overall, we found mixed support for LGCH and for the first time found that genome size is associated with plasticity, a trait widely regarded as important to invasion success.
Mangroves is an umbrella term for plants located across the tropics and sub-tropics that live in the coastal region, between the sea and the land. All mangroves evolved from terrestrial plants, providing the opportunity to assess convergence, as well as the lineage-specific features, at the genetic level. In this study, we compared chloroplast genomes from 21 mangrove species, covering main phylogenetic clades. We demonstrate that chloroplast gene order, content, and genome size is largely conserved in mangroves. The exceptions are loss of the photosystem I gene psaZ in Acanthus ilicifolius and inversion of the ribosomal protein gene rpl23 in Avicennia germinans. The repeat content of mangrove chloroplast varied between species, but was conserved within species of the same order. Sequence diversity analysis revealed that the IR (invert repeat) region was highly conserved compared to the SC (single-copy) region in most phylogenetic clades, except clade core leptosporangiates (ferns). The ribosomal protein gene rps7 was under positive selection in Kandelia obovato, Rhizophora stylosa, Bruguiera sexangular and Rhizophora mangle, a monophyletic branch of clade fabids, while no evidence of positive selection was found in other mangrove lineages. Taken together, our data suggests that convergent evolutionary dynamics leaves no significant signal on the plastid genome of mangroves. The complete chloroplast genomes provided in this study shed light on the evolution of these important plastids and provides a valuable resource for further research efforts. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.
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