Leaf Serration Research Articles

Reinstatement of the Sino-Himalayan species Senecio pentanthus (Asteraceae, Senecioneae)

Senecio pentanthus (Asteraceae, Senecioneae) has been previously placed in synonymy with Synotis triligulata. Our critical examination of herbarium specimens (including type material) and living plants of S. pentanthus demonstrates that it can be easily distinguished from Syn. triligulata by the leaf serration and the number of phyllaries and florets. We therefore reinstate the independent specific status of S. pentanthus and propose a new combination, i.e. Syn. pentantha. Lectotypification is made for Syn. pentantha herein. A key to all the known species in Syn. ser. Microglossae and Syn. vagans, a species placed in Syn. ser. Erectae but actually more closely similar to those in the former series, is provided.

Impact of erecta mutation on leaf serration differs between Arabidopsis accessions

ABSTRACTSerrations or teeth of plant leaves are a morphological trait regulated genetically and environmentally. Very recently, it has been reported that the receptor kinases encoded by three ERECTA (ER)-family genes, ER, ER-LIKE1 (ERL1) and ERL2, redundantly play a role in tooth growth in Arabidopsis thaliana. In the report, Columbia (Col) accession was used for analyses, where none of the signal mutant of the ER-family genes exhibited serration defects. The toothless, smooth leaf margin phenotype was evident only when two out of the three ER-family genes were lost. Interestingly, it has been widely recognized that the Arabidopsis accession Landsberg erecta (L.er), which carries a loss-of-function mutation in ER, develops round leaves with smaller leaf teeth. Here, we show that the functional ER transgene promotes the tooth growth in L.er to the level of Col, indicating that the er mutation in L.er is likely responsible for the reduced growth of leaf teeth. This suggests that er single mutation affects tooth growth in a different manner between Col and L.er backgrounds, though the molecular basis for this background-dependent effect remains to be addressed.

Arabidopsis Type II Phosphatidylinositol 4-Kinase PI4Kγ5 Regulates Auxin Biosynthesis and Leaf Margin Development through Interacting with Membrane-Bound Transcription Factor ANAC078.

Normal leaf margin development is important for leaf morphogenesis and contributes to diverse leaf shapes in higher plants. We here show the crucial roles of an atypical type II phosphatidylinositol 4-kinase, PI4Kγ5, in Arabidopsis leaf margin development. PI4Kγ5 presents a dynamics expression pattern along with leaf development and a T-DNA mutant lacking PI4Kγ5, pi4kγ5–1, presents serrated leaves, which is resulted from the accelerated cell division and increased auxin concentration at serration tips. Studies revealed that PI4Kγ5 interacts with and phosphorylates a membrane-bound NAC transcription factor, ANAC078. Previous studies demonstrated that membrane-bound transcription factors regulate gene transcription by undergoing proteolytic process to translocate into nucleus, and ANAC078 undergoes proteolysis by cleaving off the transmembrane region and carboxyl terminal. Western blot analysis indeed showed that ANAC078 deleting of carboxyl terminal is significantly reduced in pi4kγ5–1, indicating that PI4Kγ5 is important for the cleavage of ANAC078. This is consistent with the subcellular localization observation showing that fluorescence by GFP-ANAC078 is detected at plasma membrane but not nucleus in pi4kγ5–1 mutant and that expression of ANAC078 deleting of carboxyl terminal, driven by PI4Kγ5 promoter, could rescue the leaf serration defects of pi4kγ5–1. Further analysis showed that ANAC078 suppresses the auxin synthesis by directly binding and regulating the expression of auxin synthesis-related genes. These results indicate that PI4Kγ5 interacts with ANAC078 to negatively regulate auxin synthesis and hence influences cell proliferation and leaf development, providing informative clues for the regulation of in situ auxin synthesis and cell division, as well as the cleavage and functional mechanism of membrane-bound transcription factors.

Regulation of MicroRNA-Mediated Developmental Changes by the SWR1 Chromatin Remodeling Complex.

The ATP-dependent SWR1 chromatin remodeling complex (SWR1-C) exchanges the histone H2A-H2B dimer with the H2A.Z-H2B dimer, producing variant nucleosomes. Arabidopsis thaliana SWR1-C contributes to the active transcription of many genes, but also to the repression of genes that respond to environmental and developmental stimuli. Unlike other higher eukaryotic H2A.Z deposition mutants (which are embryonically lethal), Arabidopsis SWR1-C component mutants, including arp6, survive and display a pleiotropic developmental phenotype. However, the molecular mechanisms of early flowering, leaf serration, and the production of extra petals in arp6 have not been completely elucidated. We report here that SWR1-C is required for miRNA-mediated developmental control via transcriptional regulation. In the mutants of the components of SWR1-C such as arp6, sef, and pie1, miR156 and miR164 levels are reduced at the transcriptional level, which results in the accumulation of target mRNAs and associated morphological changes. Sequencing of small RNA libraries confirmed that many miRNAs including miR156 decreased in arp6, though some miRNAs increased. The arp6 mutation suppresses the accumulation of not only unprocessed primary miRNAs, but also miRNA-regulated mRNAs in miRNA processing mutants, hyl1 and serrate, which suggests that arp6 has a transcriptional effect on both miRNAs and their targets. We consistently detected that the arp6 mutant exhibits increased nucleosome occupancy at the tested MIR gene promoters, indicating that SWR1-C contributes to transcriptional activation via nucleosome dynamics. Our findings suggest that SWR1-C contributes to the fine control of plant development by generating a balance between miRNAs and target mRNAs at the transcriptional level.

Reduced expression of AtNUP62 nucleoporin gene affects auxin response in Arabidopsis.

BackgroundThe plant nuclear pore complex has strongly attracted the attention of the scientific community during the past few years, in particular because of its involvement in hormonal and pathogen/symbiotic signalling. In Arabidopsis thaliana, more than 30 nucleoporins have been identified, but only a few of them have been characterized. Among these, AtNUP160, AtNUP96, AtNUP58, and AtTPR have been reported to modulate auxin signalling, since corresponding mutants are suppressors of the auxin resistance conferred by the axr1 (auxin-resistant) mutation. The present work is focused on AtNUP62, which is essential for embryo and plant development. This protein is one of the three nucleoporins (with AtNUP54 and AtNUP58) of the central channel of the nuclear pore complex.ResultsAtNUP62 promoter activity was detected in many organs, and particularly in the embryo sac, young germinating seedlings and at the adult stage in stipules of cauline leaves. The atnup62-1 mutant, harbouring a T-DNA insertion in intron 5, was identified as a knock-down mutant. It displayed developmental phenotypes that suggested defects in auxin transport or responsiveness. Atnup62 mutant plantlets were found to be hypersensitive to auxin, at the cotyledon and root levels. The phenotype of the AtNUP62-GFP overexpressing line further supported the existence of a link between AtNUP62 and auxin signalling. Furthermore, the atnup62 mutation led to an increase in the activity of the DR5 auxin-responsive promoter, and suppressed the auxin-resistant root growth and leaf serration phenotypes of the axr1 mutant.ConclusionAtNUP62 appears to be a major negative regulator of auxin signalling. Auxin hypersensitivity of the atnup62 mutant, reminding that of atnup58 (and not observed with other nucleoporin mutants), is in agreement with the reported interaction between AtNUP62 and AtNUP58 proteins, and suggests closely related functions. The effect of AtNUP62 on auxin signalling likely occurs in relation to scaffold proteins of the nuclear pore complex (AtNUP160, AtNUP96 and AtTPR).Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-015-0695-y) contains supplementary material, which is available to authorized users.

Multiscale quantification of morphodynamics: MorphoLeaf software for 2D shape analysis.

A major challenge in morphometrics is to analyse complex biological shapes formed by structures at different scales. Leaves exemplify this challenge as they combine differences in their overall shape with smaller shape variations at their margin, leading to lobes or teeth. Current methods based on contour or on landmark analysis are successful in quantifying either overall leaf shape or leaf margin dissection, but fail in combining the two. Here, we present a comprehensive strategy and its associated freely available platform for the quantitative, multiscale analysis of the morphology of leaves with different architectures. For this, biologically relevant landmarks are automatically extracted and hierarchised, and used to guide the reconstruction of accurate average contours that properly represent both global and local features. Using this method, we establish a quantitative framework of the developmental trajectory of Arabidopsis leaves of different ranks and retrace the origin of leaf heteroblasty. When applied to different mutant forms, our method can contribute to a better understanding of gene function, as we show here for the role of CUC2 during Arabidopsis leaf serration. Finally, we illustrate the wider applicability of our tool by analysing hand morphometrics.

Biometric features and content of phenolic compounds of roseroot (Rhodiola rosea L.)

Roseroot (<em>Rhodiola rosea</em> L.) belongs to important herbs in folk medicine of Scandinavia, Russia, Mongolia, and China. Its therapeutic usage is mainly associated with the adaptogenic properties of this species. Roseroot is characterized by high morphological, phytochemical, and genetic differentiation. The aim of the present work was to determine the biometric and phytochemical co-variability of this taxon. Samples of <em>Rh. rosea</em> were collected from 4-year-old experimental field cultivation established by rhizome division in western Poland. For each plant, the biometric measurements of the clumps, shoots, leaves, and rhizomes with roots were carried out. In the underground plant parts (raw material), the contents of the main active compounds (phenylpropanoids, phenylethanoids, phenolic acids, and catechins) were determined by the HPLC-DAD method. <em>K</em>-means clustering analysis showed three well-separated plant groups of <em>Rh. rosea</em> that differed significantly in the level of most of the investigated components. It was interesting that in the raw material with a high content of phenylethanoids, a low level of phenyl­propanoids was found, and vice versa. These chemical groups clearly differed in luxuriance of plants, too. The important diagnostic feature was also the degree of leaf serration. The morphological and phytochemical co-variability of roseroot was confirmed by the correlations detected between some active compounds (especially catechins and rosavin) and biometric traits describing the size and serration of leaves, the size of clumps and shoots as well as the weight of the raw material.

Auxin influx importers modulate serration along the leaf margin.

SummaryLeaf shape in Arabidopsis is modulated by patterning events in the margin that utilize a PIN‐based auxin exporter/CUC2 transcription factor system to define regions of promotion and retardation of growth, leading to morphogenesis. In addition to auxin exporters, leaves also express auxin importers, notably members of the AUX1/LAX family. In contrast to their established roles in embryogenesis, lateral root and leaf initiation, the function of these transporters in leaf development is poorly understood. We report that three of these genes (AUX1, LAX1 and LAX2) show specific and dynamic patterns of expression during early leaf development in Arabidopsis, and that loss of expression of all three genes is required for observation of a phenotype in which morphogenesis (serration) is decreased. We used these expression patterns and mutant phenotypes to develop a margin‐patterning model that incorporates an AUX1/LAX1/LAX2 auxin import module that influences the extent of leaf serration. Testing of this model by margin‐localized expression of axr3–1 (AXR17) provides further insight into the role of auxin in leaf morphogenesis.

Strigolactones contribute to shoot elongation and to the formation of leaf margin serrations in Medicago truncatula R108.

Strigolactones were recently identified as a new class of plant hormones involved in the control of shoot branching. The characterization of strigolactone mutants in several species has progressively revealed their contribution to several other aspects of development in roots and shoots. In this article, we characterize strigolactone-deficient and strigolactone-insensitive mutants of the model legume Medicago truncatula for aerial developmental traits. The most striking mutant phenotype observed was compact shoot architecture. In contrast with what was reported in other species, this could not be attributed to enhanced shoot branching, but was instead due to reduced shoot elongation. Another notable feature was the modified leaf shape in strigolactone mutants: serrations at the leaf margin were smaller in the mutants than in wild-type plants. This phenotype could be rescued in a dose-dependent manner by exogenous strigolactone treatments of strigolactone-deficient mutants, but not of strigolactone-insensitive mutants. Treatment with the auxin transport inhibitor N-1-naphthylphtalamic acid resulted in smooth leaf margins, opposite to the effect of strigolactone treatment. The contribution of strigolactones to the formation of leaf serrations in M. truncatula R108 line represents a novel function of these hormones, which has not been revealed by the analysis of strigolactone mutants in other species.

Temporal Control of Leaf Complexity by miRNA-Regulated Licensing of Protein Complexes

The tremendous diversity of leaf shapes has caught the attention of naturalists for centuries. In addition to interspecific and intraspecific differences, leaf morphologies may differ in single plants according to age, a phenomenon known as heteroblasty. In Arabidopsis thaliana, the progression from the juvenile to the adult phase is characterized by increased leaf serration. A similar trend is seen in species with more complex leaves, such as the A. thaliana relative Cardamine hirsuta, in which the number of leaflets per leaf increases with age. Although the genetic changes that led to the overall simpler leaf architecture in A. thaliana are increasingly well understood, less is known about the events underlying age-dependent changes within single plants, in either A. thaliana or C. hirsuta. Here, we describe a conserved miRNA transcription factor regulon responsible for an age-dependent increase in leaf complexity. In early leaves, miR319-targeted TCP transcription factors interfere with the function of miR164-dependent and miR164-independent CUC proteins, preventing the formation of serrations in A. thaliana and of leaflets in C. hirsuta. As plants age, accumulation of miR156-regulated SPLs acts as a timing cue that destabilizes TCP-CUC interactions. The destabilization licenses activation of CUC protein complexes and thereby the gradual increase of leaf complexity in the newly formed organs. These findings point to posttranslational interaction between unrelated miRNA-targeted transcription factors as a core feature of these regulatory circuits.

<p align="left">Huperzia nanlingensis (Lycopodiaceae), a new terrestrial firmoss from southern China

Huperzia nanlingensis sp. nov. (Lycopodiaceae) is described as a new species from southern China. The distinguishing characters, description, ecology, conservation status, detailed illustrations and photographs are provided. The species resembles H. serrata in leaf shape and serrations on the margin of leaves. However, it is clearly separated as a distinct species on the basis of quantitative morphology, anatomy, and molecular evidence. Although the observed morphological differences between these two species are superficially subtle, H. nanlingensis can be distinguished from H. serrata by purple coloration at the tip and base of leaves, higher number of teeth on one side of the tropophyll, higher seasonal index and slightly crispate leaf margin.

The Bitter and the Sweet: Inference of Homology and Evolution of Leaf Glands inPrunus(Rosaceae) through Anatomy, Micromorphology, and Ancestral–Character State Reconstruction

Distinctive and diagnostic leaf glands occur in diverse forms and positions in Prunus. However, barely any studies have been conducted to document and examine these forms. Leaf glands in Prunus species may occur as raised structures on the leaf margin, as flattened structures on the abaxial surface, or at the tips of leaf teeth. Dark punctate spots on the abaxial surface of some tropical species have been assumed to be glandular as well. Our results show that the raised glands on the leaf margin and the flat glands on the abaxial surface share similar anatomy with extrafloral nectaries, while glands on the leaf teeth are structurally similar to colleters. Leaf glands in Prunus can be divided into class 1A (raised, marginal) and class 1B (flat, laminar) extrafloral nectaries and class 2 (leaf-teeth colleters). The derived flat glands likely evolved as a result of an adaptive loss of leaf serrations in warmer climates, while the plesiomorphic glandular-teeth condition is indirectly selected for in cooler cl...

Inheritance Beyond Plain Heritability: Variance-Controlling Genes in Arabidopsis thaliana

The phenotypic effect of a gene is normally described by the mean-difference between alternative genotypes. A gene may, however, also influence the phenotype by causing a difference in variance between genotypes. Here, we reanalyze a publicly available Arabidopsis thaliana dataset [1] and show that genetic variance heterogeneity appears to be as common as normal additive effects on a genomewide scale. The study also develops theory to estimate the contributions of variance differences between genotypes to the phenotypic variance, and this is used to show that individual loci can explain more than 20% of the phenotypic variance. Two well-studied systems, cellular control of molybdenum level by the ion-transporter MOT1 and flowering-time regulation by the FRI-FLC expression network, and a novel association for Leaf serration are used to illustrate the contribution of major individual loci, expression pathways, and gene-by-environment interactions to the genetic variance heterogeneity.

DEVELOPMENT-RELATED PcG TARGET IN THE APEX 4 controls leaf margin architecture in Arabidopsis thaliana

In a reverse genetics screen based on a group of genes enriched for development-related Polycomb group targets in the apex (DPAs), we isolated DPA4 as a novel regulator of leaf margin shape. T-DNA insertion lines in the DPA4 locus display enhanced leaf margin serrations and enlarged petals, whereas overexpression of DPA4 results in smooth margins. DPA4 encodes a putative RAV (Related to ABI3/VP1) transcriptional repressor and is expressed in the lateral organ boundary region and in the sinus of leaf serrations. DPA4 expression domains overlap with those of the known leaf shape regulator CUP-SHAPED COTYLEDON 2 (CUC2) and we provide evidence that DPA4 negatively regulates CUC2 expression independently of MIR164A, an established regulator of CUC2. Taken together, the data suggest DPA4 as a newly identified player in the signalling network that controls leaf serrations in Arabidopsis thaliana.

Native environment modulates leaf size and response to simulated foliar shade across wild tomato species.

The laminae of leaves optimize photosynthetic rates by serving as a platform for both light capture and gas exchange, while minimizing water losses associated with thermoregulation and transpiration. Many have speculated that plants maximize photosynthetic output and minimize associated costs through leaf size, complexity, and shape, but a unifying theory linking the plethora of observed leaf forms with the environment remains elusive. Additionally, the leaf itself is a plastic structure, responsive to its surroundings, further complicating the relationship. Despite extensive knowledge of the genetic mechanisms underlying angiosperm leaf development, little is known about how phenotypic plasticity and selective pressures converge to create the diversity of leaf shapes and sizes across lineages. Here, we use wild tomato accessions, collected from locales with diverse levels of foliar shade, temperature, and precipitation, as a model to assay the extent of shade avoidance in leaf traits and the degree to which these leaf traits correlate with environmental factors. We find that leaf size is correlated with measures of foliar shade across the wild tomato species sampled and that leaf size and serration correlate in a species-dependent fashion with temperature and precipitation. We use far-red induced changes in leaf length as a proxy measure of the shade avoidance response, and find that shade avoidance in leaves negatively correlates with the level of foliar shade recorded at the point of origin of an accession. The direction and magnitude of these correlations varies across the leaf series, suggesting that heterochronic and/or ontogenic programs are a mechanism by which selective pressures can alter leaf size and form. This study highlights the value of wild tomato accessions for studies of both morphological and light-regulated development of compound leaves, and promises to be useful in the future identification of genes regulating potentially adaptive plastic leaf traits.

Influence of human disturbance on patterns of leaf herbivory at Gazi Bay mangrove forest, Kenya

Mangrove herbivores cause leaf serration, perforation and galls prior to leaf abscission. This study compared damage by herbivores on leaves of four mangrove species at sites under different levels of human physical disturbance, and provides further evidence of the indirect effects of man on these valuable habitats. From 2001 to 2003 leaves collected fortnightly using litter traps were examined for evidence of herbivore damage, e.g. holes, margin damage, and a mix of both holes and margin damage on the leaf, and compared using ANOVA. Of 10 600 leaves examined, 3 604 had evidence of herbivore attack, with margin damage being most prevalent (60%). On Rhizophora mucronata, holes and mixed damage occurred on over 30% of damaged leaves, while margin damage was common to all other species examined. Leaf attack intensity was 14% lower at undisturbed sites, with margin damage being most common. Comparison between corresponding mangrove forest sites in Kenya showed significant increase in margin damage and concurrent decline in holes and mixed damage at disturbed sites. Variation in leaf damage occurrence was attributed to changes in forest structural and biological complexity owing to selective harvesting of flora and fauna that influenced the competitive ability and prevalence of aerial herbivorous guild.

A newly recorded naturalized species in Korea: Prunus speciosa (Koidz.) Nakai (Rosaceae, Prunoideae)

Prunus speciosa (Koidz.) Nakai belonging to Prunoideae of Rosaceae, a species previously unrecorded in Korean flora, is described. Prunus speciosa (Koidz.) Nakai is similar to Prunus sargentii Rehder and Prunus jamasakura Siebold ex Koidz., but different because it has toothed lobes of calyx tubes with the apex of leaf serrations aristate. This species is naturalized widely in the eastern parts of Jeju Island but is endemic to Japan.

Flow-plant interactions at a leaf scale: effects of leaf shape, serration, roughness and flexural rigidity

The effects of leaf shape, serration, roughness and flexural rigidity on drag force imposed by flowing water and its time variability were experimentally studied in an open-channel flume at seven leaf Reynolds numbers ranging from 5 to 35 × 103. The study involved artificial leaves of the same surface area but with three shapes (‘elliptic’, ‘rectangular’ and ‘pinnate’), three flexural rigidities, smooth-edge and sawtooth-like serration, and three combinations of surface roughness (two-side rough, one-side rough/one-side smooth, and two-side smooth). Shape was the most important factor determining flow-leaf interactions, with flexural rigidity, serration and surface roughness affecting the magnitude but not the direction of the effect on drag control. The smooth-edge elliptic leaf had a better hydrodynamic shape as it experienced less drag force, with the rectangular leaf showing slightly less efficiency. The pinnate leaf experienced higher drag force than the other leaves due to its complex geometry. It is likely that flow separation from 12 leaflets of the pinnate leaf prevented leaf reconfiguration such as leaflets folding and/or streamlining. Flexural rigidity strongly influenced the leaf reconfiguration and augmented the serration effect since very rigid leaves showed a strong effect of serration. Furthermore, serration changed the turbulence pattern around the leaves by increasing the turbulence intensity. Surface roughness was observed to enhance the drag force acting on the leaf at high Reynolds numbers. The results also suggest that there are two distinctly different flow-leaf interaction regimes: (I) regime of passive interaction at low turbulence levels when the drag statistics are completely controlled by the turbulence statistics, and (II) regime of active interaction at high turbulence levels when the effect of leaf properties on the drag statistics becomes comparable to the turbulence contribution.

Developmental Analysis of aMedicago truncatula smooth leaf margin1Mutant Reveals Context-Dependent Effects on Compound Leaf Development

Compound leaf development requires highly regulated cell proliferation, differentiation, and expansion patterns. We identified loss-of-function alleles at the SMOOTH LEAF MARGIN1 (SLM1) locus in Medicago truncatula, a model legume species with trifoliate adult leaves. SLM1 encodes an auxin efflux carrier protein and is the ortholog of Arabidopsis thaliana PIN-FORMED1 (PIN1). Auxin distribution is impaired in the slm1 mutant, resulting in pleiotropic phenotypes in different organs. The most striking change in slm1 is the increase in the number of terminal leaflets and a simultaneous reduction in the number of lateral leaflets, accompanied by reduced expression of SINGLE LEAFLET1 (SGL1), an ortholog of LEAFY. Characterization of the mutant indicates that distinct developmental domains exist in the formation of terminal and lateral leaflets. In contrast with the pinnate compound leaves in the wild type, the slm1 sgl1 double mutant shows nonpeltately palmate leaves, suggesting that the terminal leaflet primordium in M. truncatula has a unique developmental mechanism. Further investigations on the development of leaf serrations reveal different ontogenies between distal serration and marginal serration formation as well as between serration and leaflet formation. These data suggest that regulation of the elaboration of compound leaves and serrations is context dependent and tightly correlated with the auxin/SLM1 module in M. truncatula.

Ectopic expression of the Arabidopsis MINI ZINC FINGER1 and MIF3 genes induces shoot meristems on leaf margins

A leaf undergoes determinate growth from a primordium on flank of the shoot apical meristem. Several intrinsic pathways restrict meristematic activity in the leaf of Arabidopsis; however, other factors remain to be defined. We report here that the overexpression of MINI ZINC FINGER1 (MIF1) or MIF3 disrupted the leaf determinate growth by inducing ectopic shoot meristems on leaf margins. These ectopic meristems occurred along margins of late rosette leaves at serration sinuses in an ERECTA-dependent manner. Expression of STM was activated in these ectopic meristems but not other leaf regions. The formation of ectopic meristems was independent of the BP gene but suppressed by exogenous gibberellic acid. In addition, reduced auxin response along leaf margins and subsequent response peak in the sinus were correlated with the occurrence of ectopic meristems. Our results suggest that the sinus of leaf serration is a quiescent domain possessing the potential for meristem formation. MIF1- or MIF3-overexpressing transgenic plants may provide a new genetic system for dissecting the molecular mechanism that maintains leaf determinate growth, and for understanding the interactions between hormone actions and meristematic activity.