Early Plant Life Research Articles

Environmental Effects during Early Life-History Stages and Seed Development on Seed Functional Traits of an Australian Native Legume Species.

Understanding how seed functional traits interact with environmental factors to determine seedling recruitment is critical to assess the impact of climate change on ecosystem restoration. This study focused on the effects of environmental factors on the mother plant during early plant life history stages and during seed development. Desmodium brachypodum A. Gray (large tick trefoil, Fabaceae) was used as a model species. Firstly, this study analyzed seed germination traits in response to temperature and moisture stress. Secondly, it investigated how seed burial depth interacts with temperature and soil moisture to influence seedling emergence traits. Finally, it determined if contrasting levels of post-anthesis soil moisture could result in changes in D. brachypodum reproductive biology and seed and seedling functional traits. The results showed that elevated temperature and moisture stress interacted to significantly reduce the seed germination and seedling emergence (each by >50%), while the seed burial improved the seedling emergence. Post-anthesis soil moisture stress negatively impacted the plant traits, reducing the duration of the reproductive phenology stage (by 9 days) and seed production (by almost 50%). Unexpectedly, soil moisture stress did not affect most seed or seedling traits. In conclusion, elevated temperatures combined with low soil moisture caused significant declines in seed germination and seedling emergence. On the other hand, the reproductive output of D. brachypodum had low seed variability under soil moisture stress, which might be useful when sourcing seeds from climates with high variability. Even so, a reduction in seed quantity under maternal moisture stress can impact the long-term survival of restored plant populations.

MSP1 encodes an essential RNA-binding pentatricopeptide repeat factor required for nad1 maturation and complex I biogenesis in Arabidopsis mitochondria.

Mitochondrial biogenesis relies on nuclearly encoded factors, which regulate the expression of the organellar-encoded genes. Pentatricopeptide repeat (PPR) proteins constitute a major gene family in angiosperms that are pivotal in many aspects of mitochondrial (mt)RNA metabolism (e.g. trimming, splicing, or stability). Here, we report the analysis of MITOCHONDRIA STABILITY/PROCESSING PPR FACTOR1 (MSP1, At4g20090), a canonical PPR protein that is necessary for mitochondrial functions and embryo development. Loss-of-function allele of MSP1 leads to seed abortion. Here, we employed an embryo-rescue method for the molecular characterization of msp1 mutants. Our analyses reveal that msp1 embryogenesis fails to proceed beyond the heart/torpedo stage as a consequence of a nad1 pre-RNA processing defect, resulting in the loss of respiratory complex I activity. Functional complementation confirmed that msp1 phenotypes result from a disruption of the MSP1 gene. In Arabidopsis, the maturation of nad1 involves the processing of three RNA fragments, nad1.1, nad1.2, and nad1.3. Based on biochemical analyses and mtRNA profiles of wild-type and msp1 plants, we concluded that MSP1 facilitates the generation of the 3' terminus of nad1.1 transcript, a prerequisite for nad1 exons a-b splicing. Our data substantiate the importance of mtRNA metabolism for the biogenesis of the respiratory system during early plant life.

Examining the spatiotemporal variation of genetic diversity and genetic rarity in the natural plant recolonization of human-altered areas

The spatiotemporal genetic variation at early plant life stages may substantially affect the natural recolonization of human-altered areas, which is crucial to understand plant and habitat conservation. In animal-dispersed plants, dispersers’ behavior may critically drive the distribution of genetic variation. Here, we examine how genetic rarity is spatially and temporally structured in seedlings of a keystone pioneer palm (Chamaerops humilis) and how the variation of genetic rarity could ultimately affect plant recruitment. We intensively monitored the seed rain mediated by two medium-sized carnivores during two consecutive seasons in a Mediterranean human-altered area. We genotyped 143 out of 309 detected seedlings using 12 microsatellite markers. We found that seedlings emerging from carnivore-dispersed seeds showed moderate to high levels of genetic diversity and no evidence of inbreeding. We found inflated kinship among seedlings that emerged from seeds within a single carnivore fecal sample, but a dilution of such FSGS at larger spatial scales (e.g. latrine). Seedlings showed a significant genetic sub-structure and the sibling relationships varied depending on the spatial scale. Rare genotypes arrived slightly later throughout the dispersal season and tended to be spatially isolated. However, genetic rarity was not a significant predictor by itself which indicates that, at least, its influence on seedling survival was smaller than other spatiotemporal factors. Our results suggest strong C. humilis resilience to genetic bottlenecks due to human disturbances. We highlight the study of plant-animal interactions from a genetic perspective since it provides crucial information for plant conservation and the recovery of genetic plant resilience.

Group II Intron-Encoded Proteins (IEPs/Maturases) as Key Regulators of Nad1 Expression and Complex I Biogenesis in Land Plant Mitochondria.

Mitochondria are semi-autonomous organelles that produce much of the energy required for cellular metabolism. As descendants of a bacterial symbiont, most mitochondria harbor their own genetic system (mtDNA/mitogenome), with intrinsic machineries for transcription and protein translation. A notable feature of plant mitochondria involves the presence of introns (mostly group II-type) that reside in many organellar genes. The splicing of the mtRNAs relies on the activities of various protein cofactors, which may also link organellar functions with cellular or environmental signals. The splicing of canonical group II introns is aided by an ancient class of RT-like enzymes (IEPs/maturases, MATs) that are encoded by the introns themselves and act specifically on their host introns. The plant organellar introns are degenerated in structure and are generally also missing their cognate intron-encoded proteins. The factors required for plant mtRNA processing are mostly nuclearly-encoded, with the exception of a few degenerated MATs. These are in particular pivotal for the maturation of NADH-dehydrogenase transcripts. In the following review we provide an update on the non-canonical MAT factors in angiosperm mitochondria and summarize the current knowledge of their essential roles in regulating Nad1 expression and complex I (CI) biogenesis during embryogenesis and early plant life.

NMAT3 is an essential maturase splicing factor required for holo-complexI biogenesis and embryo development in Arabidopsis thaliana plants.

Group-II introns are self-splicing mobile genetic elements consisting of catalytic intron-RNA and its related intron-encoded splicing maturase protein cofactor. Group-II sequences are particularly plentiful within the mitochondria of land plants, where they reside within many critical gene loci. During evolution, the plant organellar introns have degenerated, such as they lack regions that are are required for splicing, and also lost their evolutionary related maturase proteins. Instead, for their splicing the organellar introns in plants rely on different host-acting protein cofactors, which may also provide a means to link cellular signals with respiratory functions. The nuclear genome of Arabidopsis thaliana encodes four maturase-related factors. Previously, we showed that three of the maturases, nMAT1, nMAT2 and nMAT4, function in the excision of different group-II introns in Arabidopsis mitochondria. The function of nMAT3 (encoded by the At5g04050 gene locus) was found to be essential during early embryogenesis. Using a modified embryo-rescue method, we show that nMAT3-knockout plants are strongly affected in the splicing of nad1 introns1, 3 and 4 in Arabidopsis mitochondria, resulting in complex-I biogenesis defects and altered respiratory activities. Functional complementation of nMAT3 restored the organellar defects and embryo-arrested phenotypes associated with the nmat3 mutant line. Notably, nMAT3 and nMA4 were found to act on the same RNA targets but have no redundant functions in the splicing of nad1 transcripts. The two maturases, nMAT3 and nMAT4 are likely to cooperate together in the maturation of nad1 pre-RNAs. Our results provide important insights into the roles of maturases in mitochondria gene expression and the biogenesis of the respiratory system during early plant life.

Differential Interspecific Adaptation to Abiotic Stress by Plantago Species

The success of seed-based conservation and restoration efforts using native plant species is largely determined by ensuring two key life history transitions are accommodated. These are from “seed to germinated seed” and “germinated seed to established seedling.” In turn, optimization of these life history transitions is determined by a “genetic × environmental” interaction and later largely characterized by localized climatic (abiotic) conditions. It is these environmental stress factors that can act as natural selection agents for specific plant–trait combinations, or phenotypes. In turn, such adaptation may also limit a species range. To test the relationship between these two early plant life history stage transitions, “seed to germinated seed” and “germinated seed to established seedling,” the attributes were characterized for two species of Plantago that occupy contrasting environments and since these species have potential for native seed-based habit restoration and conservation. The species were Plantago coronopus (L.), localized at lower and drier altitudes, and Plantago lanceolata (L.), characterized as occupying higher and wetter altitudinal clines. Seeds were collected from 20 accessions of six natural populations spanning four European countries for both P. lanceolata and P. coronopus. Seed germination (G) and seedling establishment (S) data were determined at six temperatures (T) and six water potentials (Ψ), and the data obtained were analyzed using a generalized linear model (GLM). The results indicate that P. coronopus has adapted physiologically to its high-altitude conditions such that seed germination and seedling establishment may be more readily achieved in this cooler environment where water is less limiting. In contrast, the lower θT of P. lanceolata better facilitates more efficient seed germination and seedling establishment in drier and warmer clines of lower altitude. In addition to establishing a genotypic (species) underpin for seed and seedling trait differences observed, the insights gained may also be exploited to best deploy each species in situ for seed-based conservation and restoration efforts.

Why so Complex? The Intricacy of Genome Structure and Gene Expression, Associated with Angiosperm Mitochondria, May Relate to the Regulation of Embryo Quiescence or Dormancy-Intrinsic Blocks to Early Plant Life.

Mitochondria play key roles in cellular-energy metabolism and are vital for plant-life, such as for successful germination and early-seedling establishment. Most mitochondria contain their own genetic system (mtDNA, mitogenome), with an intrinsic protein-synthesis machinery. Although the challenges of maintaining prokaryotic-type structures and functions are common to Eukarya, land plants possess some of the most complex organelle composition of all known organisms. Angiosperms mtDNAs are characteristically the largest and least gene-dense among the eukaryotes. They often contain highly-variable intergenic regions of endogenous or foreign origins and undergo frequent recombination events, which result in different mtDNA configurations, even between closely-related species. The expression of the mitogenome in angiosperms involves extensive mtRNA processing steps, including numerous editing and splicing events. Why do land-plant’s mitochondria have to be so complex? The answer to this remains a matter of speculation. We propose that this complexity may have arisen throughout the terrestrialization of plants, as a means to control embryonic mitochondrial functions —a critical adaptive trait to optimize seed germination. The unique characteristics of plant mtDNA may play pivotal roles in the nuclear-regulation of organellar biogenesis and metabolism, possibly to control embryos quiescence or dormancy, essential determinants for the establishment of viable plantlets that can survive post-germination.

Effects of climate warming and prolonged snow cover on phenology of the early life history stages of four alpine herbs on the southeastern Tibetan Plateau.

Much research has focused on plant responses to ongoing climate change, but there is relatively little information about how climate change will affect the early plant life history stages. Understanding how global warming and changes in winter snow pattern will affect seed germination and seedling establishment is crucial for predicting future alpine population and vegetation dynamics. In a 2-year study, we tested how warming and alteration in the snowmelt regime, both in isolation and combination, influence seedling emergence phenology, first-year growth, biomass allocation, and survival of four native alpine perennial herbs on the southeastern Tibetan Plateau. Warming promoted seedling emergence phenology of all four species and biomass per plant of two species but reduced seedling survival of three species. Prolonged snow cover partly mediated the affects of warming on Primula alpicola (survival and biomass), Pedicularis fletcheri (phenology, biomass, and root:shoot ratio) and Meconopsis integrifolia (survival). For the narrowly distributed species M. racemosa, seedling growth was additively decreased by warming and prolonged snow cover. Both warming and alteration of the snow cover regime can influence plant recruitment by affecting seedling phenology, growth, and survival, and the effects are largely species-specific. Thus, climate change is likely to affect population dynamics and community structure of the alpine ecosystem. This is the first experimental demonstration of the phenological advancement of seedling emergence in the field by simulated climate warming.

Benzoksazinoidi - zaštitni sekundarni metaboliti žitarica - biohemija i genetička kontrola

Benzoxazinoids (1,4-benzoxazin-3(4H)-one derivatives, BXs) are plant secondary metabolites that play a crucial role in plant resistance to insects, fungi, bacteria and nematodes, and in weed suppression during early plant life. These biochemicals are constitutive compounds found in some members of the family Poaceae and have been studied in detail in maize (Zea mays L.), wheat (Triticum aestivum L.) and rye (Secale cereale L.). The most effective allelopathic benzoxazinoids are 2,4-dihydroxy-7-methoxy-2H-1,4-benzoxazin-3(4H)-one (DIMBOA) and 2,4-dihydroxy-1,4-benzoxazin-3-one (DIBOA), classified as hydroxamic acids. Aiming to draw attention to the importance of BXs in plant defence and their potential application in cereal protection, this review summarises the recent findings in genetic control, biochemical pathways, and the mode of action of these secondary metabolites and addresses unresolved questions related to BXs.

DNA methylation dynamics during early plant life

BackgroundCytosine methylation is crucial for gene regulation and silencing of transposable elements in mammals and plants. While this epigenetic mark is extensively reprogrammed in the germline and early embryos of mammals, the extent to which DNA methylation is reset between generations in plants remains largely unknown.ResultsUsing Arabidopsis as a model, we uncovered distinct DNA methylation dynamics over transposable element sequences during the early stages of plant development. Specifically, transposable elements and their relics show invariably high methylation at CG sites but increasing methylation at CHG and CHH sites. This non-CG methylation culminates in mature embryos, where it reaches saturation for a large fraction of methylated CHH sites, compared to the typical 10–20% methylation level observed in seedlings or adult plants. Moreover, the increase in CHH methylation during embryogenesis matches the hypomethylated state in the early endosperm. Finally, we show that interfering with the embryo-to-seedling transition results in the persistence of high CHH methylation levels after germination, specifically over sequences that are targeted by the RNA-directed DNA methylation (RdDM) machinery.ConclusionOur findings indicate the absence of extensive resetting of DNA methylation patterns during early plant life and point instead to an important role of RdDM in reinforcing DNA methylation of transposable element sequences in every cell of the mature embryo. Furthermore, we provide evidence that this elevated RdDM activity is a specific property of embryogenesis.

Fossil Early Psilophytian & Lycopodian, Spenopsida Lines of Evolution

Evolution of the plants is the very important aspects of the life on the planet. Since early plant life was typically aquatic in nature. It was the assemblage of the many kind of the aquatic algae’s and the other taxa’s of the aquatic importance. Among them the bryophytes are the plants which were amphibious in nature. However, the pteridophytes are typically land plants having well developed vascular bundles as well as other features of the and adaptations. Pteridophytes have the long fossils history; plants were well developed in the whole Paleozoic era. They were flourished well in the late Devonian and the carboniferous period. In that era one can find the number of the examples of fossils plants which were intimidate in evolution of the many kinds of the organs. Lepidocarpales was the assemblage of the organs like structure which have the pioneer’s symptoms of the evolution of the ovules. That review presents the assemblage of the fossil pteridophytes. \r\n

Do rhizosphere priming effects enhance plant nitrogen uptake under elevated CO2?

Numerous studies suggest that rhizosphere priming can mediate decomposition of soil organic matter (SOM), but direct evidence of priming-induced soil SOM decomposition on plant N uptake under elevated CO2 (eCO2) is very rare. By using a continuous dual labelling technique with 13C-depleted CO2 and 15N-enriched soil, we investigated priming of SOM decomposition and its relationship with plant N uptake of C4 and C3 grasses from a grassland ecosystem under eCO2. We observed that eCO2 induced increases in plant biomass, plant N uptake, rhizosphere priming, and total SOM decomposition in both grasses at an early plant life stage. Increased total SOM decomposition was positively related with plant N uptake by both C4 and C3 grasses under eCO2. However, the C3 grass was more dependent on N acquired from rhizosphere priming of SOM than the C4 grass. Our findings highlight that plant N uptake could be enhanced under eCO2 via accelerated SOM decomposition, and rhizosphere priming effects on SOM decomposition could play a more important role in N availability of the C3 grass in comparison with the C4 grass.

Faster acquisition of symbiotic partner by common mycorrhizal networks in early plant life stage

AbstractArbuscular mycorrhizal (AM) fungi usually improve plant performance yet our knowledge about their effects on seed germination and early plant establishment is very limited. We performed a factorial greenhouse experiment where the seeds from four low Arctic co‐occurring mycorrhizal herbs (Antennaria dioica, Campanula rotundifolia, Sibbaldia procumbens, and Solidago virgaurea) were germinated alone or in the vicinity of an adult Sibbaldia plant with or without AM fungi; given either as spores or being present in a common mycorrhizal network (CMN). Three different AM fungal species were examined to assess species‐specific differences in symbiont acquisition rate. Of the four plant species investigated, the presence of AM fungi affected seed germination only in Campanula and this effect was dependent on whether the AM fungi were present in the soil as spores or as a CMN. Overall, after germination, developing seedlings showed AM fungal colonization in their roots as soon as 2 d after cotyledon emergence. Our results show that CMN may provide germinating seedlings faster acquisition of the AM fungal partner in comparison to acquisition from spores. Furthermore, there were AM species‐specific differences in the symbiont acquisition rate highlighting the importance of species identity in AM interactions. These findings suggest that while AM fungi may not play a fundamental role during seed germination, plant community composition may be affected by the species‐specific AM fungal effects on seedling establishment and CMN acquisition.

Gene Expression Profile Changes in Germinating Rice

Water absorption is a prerequisite for seed germination. During imbibition, water influx causes the resumption of many physiological and metabolic processes in growing seed. In order to obtain more complete knowledge about the mechanism of seed germination, two-dimensional gel electrophoresis was applied to investigate the protein profile changes of rice seed during the first 48 h of imbibition. Thirty-nine differentially expressed proteins were identified, including 19 down-regulated and 20 up-regulated proteins. Storage proteins and some seed development- and desiccation-associated proteins were down regulated. The changed patterns of these proteins indicated extensive mobilization of seed reserves. By contrast, catabolism-associated proteins were up regulated upon imbibition. Semi-quantitative real time polymerase chain reaction analysis showed that most of the genes encoding the down- or up-regulated proteins were also down or up regulated at mRNA level. The expression of these genes was largely consistent at mRNA and protein levels. In providing additional information concerning gene regulation in early plant life, this study will facilitate understanding of the molecular mechanisms of seed germination.

Breeding system and early stage inbreeding depression in a Nova Scotian population of the global rarity, Sabatia kennedyana (Gentianaceae)

Abstract The survival of populations of rare plant species may be affected both by total levels of seed production and by inbreeding depression expressed upon self-fertilization. We examined natural seed production and rates of self-fertilization in a Nova Scotian lakeshore population of the globally rare Atlantic Coastal Plain plant, Sabatia kennedyana Fernald (Gentianaceae), and determined the effect of self and cross pollinations on fitness at early plant life stages. Seed production was not limited by natural pollination levels. Furthermore, flowers from which pollinators were excluded produced 66% as many seeds as unprotected, naturally pollinated plants, indicating that substantial seed set can occur in the absence of pollinators. The selfing rate of naturally pollinated flowers was estimated as 21% using the inbreeding depression method. Stage-specific inbreeding depression was 19% at germination, and cumulative inbreeding depression from fertilization through germination was 23%. Seed formation (s...

GENSEL, P. G. & EDWARDS, D. (eds) 2001. Plants Invade the Land. Evolutionary & Environmental Perspectives. Critical Moments & Perspectives in Paleobiology and Earth History Series. xi + 304 pp. New York: Columbia University Press. Price £46.50 (hard covers). ISBN 0 231 11160 6

GENSEL, P. G. & EDWARDS, D. (eds) 2001. Plants Invade the Land. Evolutionary & Environmental Perspectives. Critical Moments & Perspectives in Paleobiology and Earth History Series. xi + 304 pp. New York: Columbia University Press. Price £46.50 (hard covers). ISBN 0 231 11160 6 - Volume 140 Issue 4