Biology subjects

Poethig, R. S.

Publications and source records attributed to Poethig, R. S..

7 recordsLinked to original sources

bioRxiv2025

Heterchronic shifts in a timing-keeping microRNA are associated with multiple instances of neoteny in plants

The prolonged production of juvenile traits and an associated reduction or loss of adult traits during development (neoteny) can either arise from a change in genes that mediate the timing of the shift between juvenile and adult traits (timing genes) or from changes in genes that are necessary for the development of adult traits (response genes). To date, the relative contribution of each developmental mechanism to the origins of neoteny remain unclear. We examined this question in the plant genus, Acacia, which contains species that undergo the juvenile-to-adult vegetative transition (vegetative phase change) early in shoot development, as well as species that remain permanently juvenile, or have delayed vegetative phase change. Mapping the timing of vegetative phase change onto a molecular phylogeny of Acacia revealed that permanent juvenility has evolved multiple times and is sometimes associated with a delay in vegetative phase change in related species. In three cases, the absence or delay in vegetative phase change was associated with either higher amounts or a delayed decline in level of miR156, the master regulator of vegetative phase change in plants. These findings support the hypothesis that neoteny in Acacia has evolved not by a loss in the capacity to produce the adult leaf phenotype, but by a change in the timing of genes that promote juvenile leaf identity. SIGNIFICANCE STATEMENTNatural variation in the timing of the juvenile-to-adult transition has been described in many plant species, but the mechanism of this variation and its contribution to plant evolution is unknown. The genus Acacia is an excellent system in which to study these questions because it includes species that produce juvenile and adult leaves, as well as species that only produce juvenile leaves. Our results suggest that many permanently juvenile leaf species in Acacia are the result of the prolonged expression of the juvenile vegetative phase, not a loss of the ability to produce an adult leaf. In at least some cases, this neotenous phenotype is associated with a change in the expression of miR156, the master regulator of vegetative phase change.

evolutionary biology↗

bioRxiv2021

Vegetative Phase Change Causes Age-Dependent Changes in Phenotypic Plasticity

O_LIPhenotypic plasticity allows organisms to optimize traits for their environment. As organisms age, they experience diverse environments that benefit from varying degrees of phenotypic plasticity. Developmental transitions can control these age-dependent changes in plasticity and as such, the timing of these transitions can determine when plasticity changes in an organism. C_LIO_LIHere we investigate how the transition from juvenile-to adult-vegetative development known as vegetative phase change (VPC) contributes to age-dependent changes in phenotypic plasticity and how the timing of this transition responds to environment using both natural accessions and mutant lines in the model plant Arabidopsis thaliana. C_LIO_LIWe found that the adult phase of vegetative development has greater plasticity in leaf morphology than the juvenile phase and confirmed that this difference in plasticity is caused by VPC using mutant lines. Further, we found that the timing of VPC, and therefore the time when increased plasticity is acquired, varies significantly across genotypes and environments. C_LIO_LIThe consistent age-dependent changes in plasticity caused by VPC suggest that VPC may be adaptive. This genetic and environmental variation in the timing of VPC indicates the potential for population-level adaptive evolution of VPC. C_LI

plant biology↗

bioRxiv2021

VAL genes regulate vegetative phase change via miR156-dependent and independent mechanisms

How organisms control when to transition between different stages of development is a key question in biology. In plants, epigenetic silencing by Polycomb repressive complex 1 (PRC1) and PRC2 plays a crucial role in promoting developmental transitions, including from juvenile-to-adult phases of vegetative growth. PRC1/2 are known to repress the master regulator of vegetative phase change, miR156, leading to the transition to adult growth, but how this process is regulated temporally is unknown. Here we investigate whether transcription factors in the VIVIPAROUS/ABI3-LIKE (VAL) gene family provide the temporal signal for the epigenetic repression of miR156. Exploiting a novel val1 allele, we found that VAL1 and VAL2 redundantly regulate vegetative phase change by controlling the overall level, rather than temporal dynamics, of miR156 expression. Furthermore, we discovered that VAL1 and VAL2 also act independently of miR156 to control this important developmental transition.

plant biology↗

bioRxiv2021

Low light intensity delays vegetative phase change in Arabidopsis thaliana

Plants that develop under low intensity light (LL) often display a phenotype known as the "shade tolerance syndrome (STS)". This syndrome is similar to the phenotype of plants in the juvenile phase of shoot development, but the basis for this similarity is unknown. We tested the hypothesis that the STS is regulated by the same mechanism that regulates the juvenile vegetative phase by examining the effect of LL on rosette development in Arabidopsis thaliana. We found that LL prolonged the juvenile vegetative phase and that this was associated with an increase the expression of the master regulators of vegetative phase change, miR156 and miR157, and a decrease in the expression of their SPL targets. Exogenous sucrose partially corrected the effect of LL on seedling development and miR156 expression. Our results suggest that the response of Arabidopsis to LL is mediated by an increase in miR156/miR157 expression and by factors that repress SPL gene expression independently of miR156/miR157, and is caused in part by a decrease in carbohydrate production. The effect of LL on vegetative phase change does not require the photoreceptors and transcription factors responsible for the shade avoidance syndrome, implying that light intensity and light quality regulate rosette development by different pathways.

developmental biology↗

bioRxiv2020

miR156-mediated changes in leaf composition lead to altered photosynthetic traits during vegetative phase change

SummaryPlant morphology and physiology change with growth and development. Some of these changes are due to change in plant size and some are the result of genetically programmed developmental transitions. In this study we investigate the role of the developmental transition, vegetative phase change (VPC), on morphological and photosynthetic changes.We used overexpression of miR156, the master regulator of VPC, to modulate the timing of VPC in Populus tremula x alba, Zea mays and Arabidopsis thaliana to determine its role in trait variation independent of changes in size and overall age.Here we find that juvenile and adult leaves in all three species photosynthesize at different rates and that these differences are due to phase-dependent changes in specific leaf area (SLA) and leaf N but not photosynthetic biochemistry. Further, we found juvenile leaves with high SLA were associated with better photosynthetic performance at low light levels.This study establishes a role for VPC in leaf composition and photosynthetic performance across diverse species and environments. Variation in leaf traits due to VPC are likely to provide distinct benefits under specific environments and, as a result, selection on the timing of this transition could be a mechanism for environmental adaptation.Competing Interest StatementThe authors have declared no competing interest.View Full Text

plant biology↗

bioRxiv2020

Vegetative phase change in Populus tremula x alba

O_LIPlants transition through juvenile and adult phases of vegetative development in a process known as vegetative phase change (VPC). In poplars (genus Populus) the differences between these stages are subtle, making it difficult to determine when this transition occurs. Previous studies of VPC in poplars have relied on plants propagated in vitro, leaving the natural progression of this process unknown. C_LIO_LIWe examined developmental morphology of seed-grown and in vitro derived Populus tremula x alba (clone 717-1B4), and compared the phenotype of these, to transgenics with manipulated miR156 expression, the master regulator of VPC. C_LIO_LIIn seed-grown plants, most traits changed from node-to-node during the first 3 months of development but remained constant after node 25. Many traits remained unchanged in clones over-expressing miR156, or were enhanced when miR156 was lowered, demonstrating their natural progression is regulated by the miR156/SPL pathway. The characteristic leaf fluttering of Populus is one of these miR156-regulated traits. C_LIO_LIVegetative development in plants grown from culture mirrored that of seed-grown plants, allowing direct comparison between plants often used in research and those found in nature. These results provide a foundation for further research on the role of VPC in the ecology and evolution of this economically important genus. C_LI

plant biology↗

bioRxiv2019

ALTERED MERISTEM PROGRAM1 regulates leaf identity independent of miR156-mediated translational repression

In Arabidopsis, loss of the carboxypeptidase, ALTERED MERISTEM PROGRAM1 (AMP1), produces an increase in the rate of leaf initiation, an enlarged shoot apical meristem and an increase in the number of juvenile leaves. This phenotype is also observed in plants with reduced levels of miR156-targeted SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL) transcription factors, suggesting that AMP1 may promote SPL activity. However, we found that the amp1 phenotype is only partially corrected by elevated SPL gene expression, and that amp1 has no significant effect on SPL transcript levels, or on the level or the activity of miR156. Although evidence from a previous study suggests that AMP1 promotes miRNA-mediated translational repression, amp1 did not prevent the translational repression of the miR156 target, SPL9, or the miR159 target, MYB33. These results suggest that AMP1 regulates vegetative phase change downstream of, or in parallel to, the miR156/SPL pathway and that it is not universally required for miRNA-mediated translational repression. Summary statementWe show that loss of the carboxypeptidase, AMP1, does not interfere with the function of miR156 or miR159, suggesting that AMP1 is not universally required for miRNA-mediated translational repression in Arabidopsis.

plant biology↗