Morpho-anatomical studies of family lamiaceae species of district Lahore, Punjab: a revision to flora of Pakistan.

BACKGROUND: This study was aimed to determine the taxonomic position and delimitation of fifteen Lamiaceae taxa using leaf epidermal morpho-anatomical features in Lahore. A main objective of the study was also the revision and upgradation of Lamiaceae taxa in the flora of Pakistan, as no details of studied species are found in the flora of Pakistan. METHODS: The examination of significant anatomical parameters, such as epidermal cell shape and size, stomatal types, guard and subsidiary cells shape and size, stomatal cavity size, trichome size and shape, oil droplets, crystals, and secretory cavity characteristics were studied using light microscopic (LM) and scanning electron microscopic (SEM) techniques. Among all the studied Lamiaceae species, these anatomical features varied significantly. Principal component analysis and correlation were done to distinguish the species' similarities. RESULTS: Most species had pentagonal and hexagonal epidermal cells with straight anticlinal wall thickness. On the adaxial surface, paracytic stomata were found in Ocimum basilicum L. and Rosmarinus officinalis L. Diacytic stomata was observed in Ajuga reptans L. and anisocytic stomata in Galeopsis tetrahit L. In the abaxial surface, trichomes were present in five species, i.e., Mentha suaveolens Ehrh. A. reptans, Thymus vulgaris L., M. haplocalyx, and Salvia splendens Ewat. In S. splendens, peltate and glandular trichomes were seen whereas, in other species, trichomes were long, unbranched glandular and had tapering ends. In adaxial side trichomes were present only in M. suaveolens, A. reptans, S. bazyntina, O. basciculum, S. splendens, S. officinalis, S. rosemarinus. In other species, trichomes were absent on the adaxial surface. In abaxial view, M. suaveolens had the largest length of trichomes, and O. basciculum had the smallest. S. splendens L. had the largest trichome width, while T. vulgaris had the smallest. CONCLUSION: Hence, according to these findings, morpho-anatomical traits are useful for identifying Lamiaceae taxa. Also, there is a need of upgradation and addition of studied taxa in flora of Pakistan comprehensively.

Micromorphological Sculptural Diversity in Foliar Epidermis and Trichomes Features among Invasive Species.

This study examines the role of light microscopic (LM) and scanning electron microscopic (SEM) micromorphological traits of the epidermis in identifying and classifying invasive plants. SEM was conducted to increase our understanding of microscopic qualities that are not visible in light microscopy and to elucidate unclear affinities among invasive species. The study examines invasive species' morphological and anatomical characteristics from the Pothohar Plateau of Pakistan for the first time. The results showed that various micromorphological features are very useful for species' accurate identification. Adaxial and abaxial surfaces of leaves showed variations in subsidiary cells, glands, anticlinal wall patterns, stomata, and epidermal cells. Epidermal cell shapes observed were irregular, elongated, rectangular, and polygonal. Epidermal cells having maximum length were calculated in Stellaria media (126.3 µm) on adaxial side. On the abaxial surface, the minimum length was noticed in Eucalyptus camaldulensis (28.5 µm). Both glandular and nonglandular trichomes were examined, ranging from unicellular to multicellular. Most of the investigated specimens of leaves were amphistomatic, while some were hypostomatic, like Alternanthera pungens, Calotropis procera, Cannabis sativa, Lantana camara, and Thevetia peruviana. Leaf epidermal morphology contains numerous useful systematic features for accurate identifications of plant species. The micromorphological attributes under observation provide a standard criterion to the researcher for identifications of invasive flora in future morpho-taxonomic studies.

Continuous directional water transport on the peristome surface of Nepenthes alata.

Numerous natural systems contain surfaces or threads that enable directional water transport. This behaviour is usually ascribed to hierarchical structural features at the microscale and nanoscale, with gradients in surface energy and gradients in Laplace pressure thought to be the main driving forces. Here we study the prey-trapping pitcher organs of the carnivorous plant Nepenthes alata. We find that continuous, directional water transport occurs on the surface of the 'peristome'--the rim of the pitcher--because of its multiscale structure, which optimizes and enhances capillary rise in the transport direction, and prevents backflow by pinning in place any water front that is moving in the reverse direction. This results not only in unidirectional flow despite the absence of any surface-energy gradient, but also in a transport speed that is much higher than previously thought. We anticipate that the basic 'design' principles underlying this behaviour could be used to develop artificial fluid-transport systems with practical applications.

Rafflesia patma Blume flower organs: histology of the epidermis and vascular structures, and a search for stomata.

MAIN CONCLUSION: A histological study of Rafflesia patma revealed the simplicity of a flower's vascular tissue and epidermal features of flower organs, including their structures and pigmentation. Rafflesia is an endophytic holoparasitic plant that infects Tetrastigma. In a previous study, we characterized the shape of the strands of an endophyte (Rafflesia patma Blume) and hypothesized their distribution. In this study, we deepened our analysis by assessing parts of flower tissue sampled during anthesis, performed surface casting of the abaxial and adaxial sides of the perigone lobe to profile their surface features, and histologically characterized the perigone lobe, perigone tube, and central column base, including the anther and cupula region. The objective of these observations was to compare tissues from different organs and the distribution of cells staining positive for tannin, suberin, and lignin. Observable features in this study were vascular and epidermal tissue. We also observed reduced vascular tissue with xylem and vascular parenchyma in multiple organs. The adaxial epidermis found in the perigone lobes and tube had papillate cells, and their function might be to assist with the emission of odor through chemical evaporation. The abaxial epidermis, also found in perigone lobes and tube, had flattened cells. These, combined with the nearby flattened parenchyma cells, especially in the outermost, early perigone lobe, might provide a tougher (stiffer) outer protective barrier for the flower. The accumulation of tannin in perigone lobes might offer protection to the flower from herbivores prior to anthesis. Although a previous observation indicated the possibility of stomata on the surface of Rafflesia flowers, no stomata were found in this study.

Comparative Analyses of the Self-Sealing Mechanisms in Leaves of Delosperma cooperi and Delosperma ecklonis (Aizoaceae).

Within the Aizoaceae, the genus Delosperma exhibits a vast diversification colonizing various ecological niches in South-Africa and showing evolutionary adaptations to dry habitats that might include rapid self-sealing. Leaves of Delosperma react to external damage by the bending or contraction of the entire leaf until wound edges are brought into contact. A study of leaf morphology and anatomy, biomechanics of entire leaves and individual tissues and self-sealing kinematics after a ring incision under low and high relative humidity (RH) was carried out comparing the closely related species Delosperma cooperi and Delosperma ecklonis, which are indigenous to semi-arid highlands and regions with an oceanic climate, respectively. For both species, the absolute contractions of the examined leaf segments ("apex", "incision", "base") were more pronounced at low RH levels. Independent of the given RH level, the absolute contractions within the incision region of D. cooperi were significantly higher than in all other segments of this species and of D. ecklonis. The more pronounced contraction of D. cooperi leaves was linked mainly to the elastic properties of the central vascular strand, which is approximately twice as flexible as that of D. ecklonis leaves.

Chemical Defoliant Promotes Leaf Abscission by Altering ROS Metabolism and Photosynthetic Efficiency in Gossypium hirsutum.

Chemical defoliation is an important part of cotton mechanical harvesting, which can effectively reduce the impurity content. Thidiazuron (TDZ) is the most used chemical defoliant on cotton. To better clarify the mechanism of TDZ promoting cotton leaf abscission, a greenhouse experiment was conducted on two cotton cultivars (CRI 12 and CRI 49) by using 100 mg L-1 TDZ at the eight-true-leaf stage. Results showed that TDZ significantly promoted the formation of leaf abscission zone and leaf abscission. Although the antioxidant enzyme activities were improved, the reactive oxygen species and malondialdehyde (MDA) contents of TDZ increased significantly compared with CK (water). The photosynthesis system was destroyed as net photosynthesis (Pn), transpiration rate (Tr), and stomatal conductance (Gs) decreased dramatically by TDZ. Furthermore, comparative RNA-seq analysis of the leaves showed that all of the photosynthetic related genes were downregulated and the oxidation-reduction process participated in leaf shedding caused by TDZ. Consequently, a hypothesis involving possible cross-talk between ROS metabolism and photosynthesis jointly regulating cotton leaf abscission is proposed. Our findings not only provide important insights into leaf shedding-associated changes induced by TDZ in cotton, but also highlight the possibility that the ROS and photosynthesis may play a critical role in the organ shedding process in other crops.

Competition for epidermal space in the evolution of leaves with high physiological rates.

Leaves with high photosynthetic capacity require high transpiration capacity. Consequently, hydraulic conductance, stomatal conductance, and assimilation capacities should be positively correlated. These traits make independent demands on anatomical space, particularly due to the propensity for veins to have bundle sheath extensions that exclude stomata from the local epidermis. We measured density and area occupation of bundle sheath extensions, density and size of stomata and subsidiary cells, and venation density for a sample of extant angiosperms and fossil and living nonangiosperm tracheophytes. For most nonangiosperms, even modest increases in vein density and stomatal conductance would require substantial reconfigurations of anatomy. One characteristic of the angiosperm syndrome (e.g. small cell sizes, etc.) is hierarchical vein networks that allow expression of bundle sheath extensions in some, but not all veins, contrasting with all-or-nothing alternatives available with the single-order vein networks in most nonangiosperms. Bundle sheath modulation is associated with higher vein densities in three independent groups with hierarchical venation: angiosperms, Gnetum (gymnosperm) and Dipteris (fern). Anatomical and developmental constraints likely contribute to the stability in leaf characteristics - and ecophysiology - seen through time in different lineages and contribute to the uniqueness of angiosperms in achieving the highest vein densities, stomatal densities, and physiological rates.

Phylogenomic analyses reveal an exceptionally high number of evolutionary shifts in a florally diverse clade of African legumes.

Detarioideae is well known for its high diversity of floral traits, including flower symmetry, number of organs, and petal size and morphology. This diversity has been characterized and studied at higher taxonomic levels, but limited analyses have been performed among closely related genera with contrasting floral traits due to the lack of fully resolved phylogenetic relationships. Here, we used four representative transcriptomes to develop an exome capture (target enrichment) bait for the entire subfamily and applied it to the Anthonotha clade using a complete data set (61 specimens) representing all extant floral diversity. Our phylogenetic analyses recovered congruent topologies using ML and Bayesian methods. Anthonotha was recovered as monophyletic contrary to the remaining three genera (Englerodendron, Isomacrolobium and Pseudomacrolobium), which form a monophyletic group sister to Anthonotha. We inferred a total of 35 transitions for the seven floral traits (pertaining to flower symmetry, petals, stamens and staminodes) that we analyzed, suggesting that at least 30% of the species in this group display transitions from the ancestral condition reconstructed for the Anthonotha clade. The main transitions were towards a reduction in the number of organs (petals, stamens and staminodes). Despite the high number of transitions, our analyses indicate that the seven characters are evolving independently in these lineages. Petal morphology is the most labile floral trait with a total of seven independent transitions in number and seven independent transitions to modification in petal types. The diverse petal morphology along the dorsoventral axis of symmetry within the flower is not associated with differences at the micromorphology of petal surface, suggesting that in this group all petals within the flower might possess the same petal identity at the molecular level. Our results provide a solid evolutionary framework for further detailed analyses of the molecular basis of petal identity.

Anatomical, Phytochemical, and Histochemical Study of Juniperus rigida Needles at Different Altitudes.

Needles of Juniperus rigida are used in Chinese traditional medicine for the treatment of brucellosis, dropsy, skin disease, and rheumatoid arthritis. This is the first study that reports anatomical structures of the J. rigida needles collected at different altitudes. The most common anatomical, phytochemical, and histochemical techniques and methods are used. The results show that anatomical structures and chemical composition change significantly at different altitudes. The main anatomical characters are significant xeromorphic structures (thick epidermis, hypodermis, and cuticle), a stomatal band, a developed vascular bundle, and a marginal resin duct. The xeromorphic structures become more pronounced with increasing altitude. The phytochemical and histochemical results demonstrate that the content of the main chemical compounds (phenols and terpenoids) basically increases at a higher elevation. Histochemical analysis localizes the phenols in epidermal cells, sponge tissue, endothelial layer cells, and stomatal bands, and the terpenoids in palisade tissue, sponge tissue, and the edge of the resin duct. This work reveals the relation between anatomy and chemistry in J. rigida needles, contributes to the quality control of its ethno-medicine, and provides the evidence to develop the commercial cultivation.

Aridification as a driver of biodiversity: a case study for the cycad genus Dioon (Zamiaceae).

Background and Aims: Aridification is considered a selective pressure that might have influenced plant diversification. It is suggested that plants adapted to aridity diversified during the Miocene, an epoch of global aridification (≈15 million years ago). However, evidence supporting diversification being a direct response to aridity is scarce, and multidisciplinary evidence, besides just phylogenetic estimations, is necessary to support the idea that aridification has driven diversification. The cycad genus Dioon (Zamiaceae), a tropical group including species occurring from humid forests to arid zones, was investigated as a promising study system to understand the associations among habitat shifts, diversification times, the evolution of leaf epidermal adaptations, and aridification of Mexico. Methods: A phylogenetic tree was constructed from seven chloroplast DNA sequences and the ITS2 spacer to reveal the relationships among 14 Dioon species from habitats ranging from humid forests to deserts. Divergence times were estimated and the habitat shifts throughout Dioon phylogeny were detected. The epidermal anatomy among Dioon species was compared and correlation tests were performed to associate the epidermal variations with habitat parameters. Key Results: Events of habitat shifts towards arid zones happened exclusively in one of the two main clades of Dioon. Such habitat shifts happened during the species diversification of Dioon, mainly during the Miocene. Comparative anatomy showed epidermal differences between species from arid and mesic habitats. The variation of epidermal structures was found to be correlated with habitat parameters. Also, most of the analysed epidermal traits showed significant phylogenetic signals. Conclusions: The diversification of Dioon has been driven by the aridification of Mexico. The Miocene timing corresponds to the expansion of arid zones that embedded the ancestral Dioon populations. As response, species in arid zones evolved epidermal traits to counteract aridity stress. This case study provides a robust body of evidence supporting the idea that aridification is an important driver of biodiversity.

Relicts of the Mid-Miocene Climatic Optimum may contribute to the floristic diversity of Japan: a case study of Pinus mikii (Pinaceae) and its extant relatives.

The epidermis of Pinus mikii leaves was studied. Pinus mikii is a fossil species from the lower Miocene to lower Pleistocene of Japan. In P. mikii, the stomata are closely set and guard cells have polar extensions of cuticle on their inner cell walls. These features suggest that P. mikii is closely related to P. luchuensis, an extant species endemic to the Ryukyu Islands of Japan. Pinus mikii also shares some epidermal characters with P. thunbergii, which is semiendemic to Japan. It is possible that P. mikii is a common ancestor of both of these extant species. The distribution of P. mikii expanded during the Mid-Miocene Climatic Optimum (MMCO), but its distribution shifted southwards as global temperatures declined. Pinus luchuensis likely speciated from the retreating population, whereas P. thunbergii arose from a population that adapted to the cooler climate. This study provides a new perspective on the contribution of MMCO relicts to the floristic diversity of Japan.

Ultrastructure of the Epidermal Cell Wall and Cuticle of Tomato Fruit (Solanum lycopersicum L.) during Development.

The epidermis plays a pivotal role in plant development and interaction with the environment. However, it is still poorly understood, especially its outer epidermal wall: a singular wall covered by a cuticle. Changes in the cuticle and cell wall structures are important to fully understand their functions. In this work, an ultrastructure and immunocytochemical approach was taken to identify changes in the cuticle and the main components of the epidermal cell wall during tomato fruit development. A thin and uniform procuticle was already present before fruit set. During cell division, the inner side of the procuticle showed a globular structure with vesicle-like particles in the cell wall close to the cuticle. Transition between cell division and elongation was accompanied by a dramatic increase in cuticle thickness, which represented more than half of the outer epidermal wall, and the lamellate arrangement of the non-cutinized cell wall. Changes in this non-cutinized outer wall during development showed specific features not shared with other cell walls. The coordinated nature of the changes observed in the cuticle and the epidermal cell wall indicate a deep interaction between these two supramolecular structures. Hence, the cuticle should be interpreted within the context of the outer epidermal wall.

Optimal allocation of leaf epidermal area for gas exchange.

A long-standing research focus in phytology has been to understand how plants allocate leaf epidermal space to stomata in order to achieve an economic balance between the plant's carbon needs and water use. Here, we present a quantitative theoretical framework to predict allometric relationships between morphological stomatal traits in relation to leaf gas exchange and the required allocation of epidermal area to stomata. Our theoretical framework was derived from first principles of diffusion and geometry based on the hypothesis that selection for higher anatomical maximum stomatal conductance (gsmax ) involves a trade-off to minimize the fraction of the epidermis that is allocated to stomata. Predicted allometric relationships between stomatal traits were tested with a comprehensive compilation of published and unpublished data on 1057 species from all major clades. In support of our theoretical framework, stomatal traits of this phylogenetically diverse sample reflect spatially optimal allometry that minimizes investment in the allocation of epidermal area when plants evolve towards higher gsmax . Our results specifically highlight that the stomatal morphology of angiosperms evolved along spatially optimal allometric relationships. We propose that the resulting wide range of viable stomatal trait combinations equips angiosperms with developmental and evolutionary flexibility in leaf gas exchange unrivalled by gymnosperms and pteridophytes.

Essential role of the E3 ubiquitin ligase nopperabo1 in schizogenous intercellular space formation in the liverwort Marchantia polymorpha.

The vast majority of land plants develop gas-exchange tissues with intercellular spaces (ICSs) connected directly to the air. Although the developmental processes of ICS have been described in detail at the morphological and ultrastructural level in diverse land plants, little is known about the molecular mechanism responsible for ICS formation. The liverwort Marchantia polymorpha develops a multilayered tissue with a large ICS (air chamber), whose formation is initiated at selected positions of epidermal cells. We isolated a mutant of M. polymorpha showing impaired air-chamber formation, nopperabo1 (nop1), from T-DNA-tagged lines. In nop1 plants, no ICS was formed; consequently, a single-layered epidermis developed on the dorsal side of the thallus. The causal gene NOP1 encodes a Plant U-box (PUB) E3 ubiquitin ligase carrying tandem ARMADILLO (ARM) repeats in the C terminus. An in vitro ubiquitination assay indicated that the NOP1 protein possesses E3 ubiquitin ligase activity in a U-box-dependent manner. Confocal microscopy and biochemical analysis showed that NOP1 was localized to the plasma membrane. Our investigation demonstrated the essential role of the PUB-ARM-type ubiquitin ligase in ICS formation in M. polymorpha, which sheds light on the molecular mechanism of schizogenous ICS formation in land plants.

Tissue-specific profiling reveals transcriptome alterations in Arabidopsis mutants lacking morphological phenotypes.

Traditional genetic analysis relies on mutants with observable phenotypes. Mutants lacking visible abnormalities may nevertheless exhibit molecular differences useful for defining gene function. To examine this, we analyzed tissue-specific transcript profiles from Arabidopsis thaliana transcription factor gene mutants with known roles in root epidermis development, but lacking a single-gene mutant phenotype due to genetic redundancy. We discovered substantial transcriptional changes in each mutant, preferentially affecting root epidermal genes in a manner consistent with the known double mutant effects. Furthermore, comparing transcript profiles of single and double mutants, we observed remarkable variation in the sensitivity of target genes to the loss of one or both paralogous genes, including preferential effects on specific branches of the epidermal gene network, likely reflecting the pathways of paralog subfunctionalization during evolution. In addition, we analyzed the root epidermal transcriptome of the transparent testa glabra2 mutant to clarify its role in the network. These findings provide insight into the molecular basis of genetic redundancy and duplicate gene diversification at the level of a specific gene regulatory network, and they demonstrate the usefulness of tissue-specific transcript profiling to define gene function in mutants lacking informative visible changes in phenotype.

Root evolution at the base of the lycophyte clade: insights from an Early Devonian lycophyte.

BACKGROUND AND AIMS: The evolution of complex rooting systems during the Devonian had significant impacts on global terrestrial ecosystems and the evolution of plant body plans. However, detailed understanding of the pathways of root evolution and the architecture of early rooting systems is currently lacking. We describe the architecture and resolve the structural homology of the rooting system of an Early Devonian basal lycophyte. Insights gained from these fossils are used to address lycophyte root evolution and homology. METHODS: Plant fossils are preserved as carbonaceous compressions at Cottonwood Canyon (Wyoming), in the Lochkovian-Pragian (∼411 Ma; Early Devonian) Beartooth Butte Formation. We analysed 177 rock specimens and documented morphology, cuticular anatomy and structural relationships, as well as stratigraphic position and taphonomic conditions. KEY RESULTS: The rooting system of the Cottonwood Canyon lycophyte is composed of modified stems that bear fine, dichotomously branching lateral roots. These modified stems, referred to as root-bearing axes, are produced at branching points of the above-ground shoot system. Root-bearing axes preserved in growth position exhibit evidence of positive gravitropism, whereas the lateral roots extend horizontally. Consistent recurrence of these features in successive populations of the plant preserved in situ demonstrates that they represent constitutive structural traits and not opportunistic responses of a flexible developmental programme. CONCLUSIONS: This is the oldest direct evidence for a rooting system preserved in growth position. These rooting systems, which can be traced to a parent plant, include some of the earliest roots known to date and demonstrate that substantial plant-substrate interactions were under way by Early Devonian time. The morphological relationships between stems, root-bearing axes and roots corroborate evidence that positive gravitropism and root identity were evolutionarily uncoupled in lycophytes, and challenge the hypothesis that roots evolved from branches of the above-ground axial system, suggesting instead that lycophyte roots arose as a novel organ.

Pollinator shifts drive petal epidermal evolution on the Macaronesian Islands bird-flowered species.

Pollinator shifts are considered to drive floral trait evolution, yet little is still known about the modifications of petal epidermal surface at a biogeographic region scale. Here we investigated how independent shifts from insects to passerine birds in the Macaronesian Islands consistently modified this floral trait (i.e. absence of papillate cells). Using current phylogenies and extensive evidence from field observations, we selected a total of 81 plant species and subspecies for petal microscopy and comparative analysis, including 19 of the 23 insular species pollinated by opportunistic passerine birds (Macaronesian bird-flowered element). Species relying on passerine birds as the most effective pollinators (bird-pollinated) independently evolved at least five times and in all instances associated with a loss of papillate cells, whereas species with a mixed pollination system (birds plus insects and/or other vertebrates) evolved at least five times in Macaronesia and papillate cells were lost in only 25% of these transitions. Our findings suggest that petal micromorphology is a labile trait during pollinator shifts and that papillate cells tend to be absent on those species where pollinators have limited mechanical interaction with flowers, including opportunistic passerine birds that forage by hovering or from the ground.

[CYTOSKELETON ORIENTATION IN THE EPIDERMAL CELLS OF ROOTS FORMED DE NOVO ON LEAF EXPLANTS UNDER CLINOROTATION].

Root anatomy, cytoskeleton orientation and cell wall thickness in cells of the roots formed de novo in vitro under clinorotation (simulated microgravity) were investigated. Structure of the embryonic roots and of the roots formed de novo in cambium cells of the leaf petiole explants was shown to be similar. Root cell differentiation in vitro under clinorotation did not differ from that in control. Changes of tubulin microtubules' orientation in the epidermis of the distal elongation zone were observed under clinorotation that seems to be associated with specific physiological properties of the cells. Under clinorotation, the tendency of cell wall thinning was detected in the root cells formed in vitro.

Anthocyanin synthesis in native and wound periderms of potato.

Skin color of red potatoes is due to accumulation of anthocyanins in the tuber periderm, a protective tissue that replaces the epidermis at an early stage of tuber development. The periderm consists of external layers of suberized phellem cells making up the skin, and internal layers of parenchyma-like phelloderm cells. Red pigmentation is an important marketing factor for red-skinned potatoes. However, injuries to the tuber surface, which are common in the potato industry, result in the development of a wound periderm that is devoid of the characteristic red coloration. To study the reason for these differences in anthocyanin accumulation, the expression level of anthocyanin biosynthesis genes and regulators was monitored in native and wound periderm using microarray analysis and quantitative polymerase chain reaction. We found significantly higher expression of the anthocyanin pathway in the phelloderm cells compared with the skin and tuber-flesh samples. However, in wound periderm, the anthocyanin pathway was strongly downregulated relative to the native periderm. This was true for two developmental stages of the native periderm--'immature', when the skin is prone to skinning injuries, and 'mature', following skin set--suggesting that anthocyanin synthesis continues postharvest. Wound-induced expression of steroidal glycoalkaloid glycosyltransferases, suberin-related 3-ketoacyl-CoA synthase and actin indicated that downregulation of the anthocyanin-specific pathway does not reflect global repression of the wound-periderm transcriptome. Loss of pigmentation may result from reduced expression of the Myb-bHLH-WD40 anthocyanin regulatory complex--a possible candidate might be the bHLH transcription factor JAF13.