Male Cones Research Articles

Alternative Oxidase Capacity of Mitochondria in Microsporophylls May Function in Cycad Thermogenesis.

Cone thermogenesis is a widespread phenomenon in cycads and may function to promote volatile emissions that affect pollinator behavior. Given their large population size and intense and durable heat-producing effects, cycads are important organisms for comprehensive studies of plant thermogenesis. However, knowledge of mitochondrial morphology and function in cone thermogenesis is limited. Therefore, we investigated these mitochondrial properties in the thermogenic cycad species Cycas revoluta Male cones generated heat even in cool weather conditions. Female cones produced heat, but to a lesser extent than male cones. Ultrastructural analyses of the two major tissues of male cones, microsporophylls and microsporangia, revealed the existence of a population of mitochondria with a distinct morphology in the microsporophylls. In these cells, we observed large mitochondria (cross-sectional area of 2 μm2 or more) with a uniform matrix density that occupied >10% of the total mitochondrial volume. Despite the size difference, many nonlarge mitochondria (cross-sectional area <2 μm2) also exhibited a shape and a matrix density similar to those of large mitochondria. Alternative oxidase (AOX) capacity and expression levels in microsporophylls were much higher than those in microsporangia. The AOX genes expressed in male cones revealed two different AOX complementary DNA sequences: CrAOX1 and CrAOX2 The expression level of CrAOX1 mRNA in the microsporophylls was 100 times greater than that of CrAOX2 mRNA. Collectively, these results suggest that distinctive mitochondrial morphology and CrAOX1-mediated respiration in microsporophylls might play a role in cycad cone thermogenesis.

Thermogenesis in male cones of four cycad species

Temperature of sporophylls from excised male cones of three species from the Zamiaceae family (Ceratozamia miqueliana, Zamia fairchildiana, and Zamia pumila) and from one species from the Cycadaceae family (Cycas siamensis) was recorded over several days in an environmental chamber. Each species exhibited a different temperature profile. C. miqueliana and Z. fairchildiana were highly thermogenic, whereas C. siamensis and Z. pumila were weakly thermogenic. In C. miqueliana, the temperature of one sporophyll rose to 10 °C above ambient while other sporophylls on the same cone only reached temperatures of 0–3 °C above ambient. Temperature rates among the different cones varied between ≈ 0.01 and 0.09 ∆ °C/h. Temperature profiles of sporophylls of Z. fairchildiana and C. siamensis were reported for the first time. Studies of thermogenesis of single sporophylls in a controlled environment provide accurate temperature measurements. Furthermore, sporophylls can be exposed to different environments and thus improve our understanding of the mechanism of thermogenesis in vivo.

A syn-ent-labdadiene derivative with a rare spiro-β-lactone function from the male cones of Wollemia nobilis

An undescribed labdane-like diterpene with a rare spiro-β-lactone function was identified from the ethanol extract of the male cones of the coniferous tree Wollemia nobilis. This spirolabdadienolide (IUPAC name: syn-ent-8(17),13-labdadien-19,18-olid-15-oic acid methyl ester; trivial name: wollemolide), was isolated by means of traditional and high performance chromatography techniques and structurally elucidated through NMR and MS. In addition, six further known metabolites were evidenced in the extract. Wollemolide, which may be considered an additional chemotaxonomic marker, and 4′-O-methyl-scutellarein, a simple flavonoid, had not been isolated in our previous phytochemical study on the same plant organ. This demonstrates how the molecular pattern of a plant species is in continuous movement and changes with the passing of time according to the climate of the year.

Ceratophila, a new genus of erotylid beetles (Erotylidae: Pharaxonothinae) inhabiting male cones of the cycad Ceratozamia (Cycadales: Zamiaceae).

Ceratophila new genus (Erotylidae: Pharaxonothinae) inhabiting male cones of the Mesoamerican cycad genus Ceratozamia Brongniart (Zamiaceae) is described for seven new species and compared to other genera of the Pharaxonothinae. Ceratophila differs from other genera of the Pharaxonothinae in many characters, most notable of which are: lateral pronotal carina thicker anteriorly in lateral view; head with supraocular and transverse occipital lines; elytra lacking a basal bead; and stridulatory files at base of head narrowly separated. Ceratophila has the male genitalia laterally compressed with a short median lobe and flagellum, similar to other Erotylidae. In comparison, the most superficially similar pharaxonothine genus Pharaxonotha Reitter has: lateral pronotal carina thin along entire length; head lacking supraocular lines, but with transverse occipital lines; elytra with distinct basal bead; stridulatory files at base of head widely separated; and unique male genitalia that are dorsoventrally flattened with a long median lobe and flagellum. Ceratophila contains two subgenera, which differ most notably in external characters and sexual dimorphism. Members of Ceratophila (Ceratophila), the nominal subgenus, have: more cylindrical bodies, pronotum evenly convex dorsally; the pronotum lacking basal longitudinal grooves on disc; metatibiae that are distinctly triangularly dilated toward apex; and no apparent external sexual dimorphism. In comparison, members of Ceratophila (Vovidesa) new subgenus have: dorsoventrally flattened bodies; the pronotum explanate (concave) along lateral margins; the pronotum with basal longitudinal grooves on disc; metatibiae weakly or not dilated toward apex; and with all tibiae in males showing strong sexual dimorphism. Four new species are described within the subgenus Ceratophila: C. (C.) chemnicki, C. (C.) gregoryi, C. (C.) picipennis, C. (C.) sanchezae; and three new species are described within the subgenus Vovidesa: C. (V.) chiapensis, C. (V.) mixeorum, C. (V.) vazquezi. Keys to genera, subgenera and species of known adults based on morphology are provided.

Macrofossil evidence unveiling evolution of male cones in Ephedraceae (Gnetidae)

BackgroundMale cones of modern Ephedraceae are compound and compact. No fossil evidence has so far been found to support an origin of the compact compound male cone from a hypothetical loosely-arranged shoot system.ResultsHere we describe a new macrofossil taxon, Eamesia chinensis Yang, Lin, Ferguson et Wang, gen. et sp. nov., from the Early Cretaceous of western Liaoning, northeastern China. It was an ephedroid shrub bearing male spikes terminal to twigs, but differs from modern Ephedraceae by its loosely-arranged male cones, the axillary male shoot consisting of an elongated synangiophore on which leaf-like foliar organs were inserted, and four sessile synangia terminal to the apex.ConclusionsThe morphology of this fossil suggests that the modern compact male cone of Ephedra was indeed derived from a once loosely-arranged shoot system, and the male reproductive unit originated from a once elongated axillary male shoot. This new fossil species thus provides a transitional link from the hypothetical ancestral shoot system to the modern compact morphology. Changes of habitat from closed humid forests to open dry deserts and shifts of the pollination syndrome may have acted as the driving forces behind this morphological evolution.

Pollination of the Australian cycad Cycas ophiolitica (Cycadaceae): the limited role of wind pollination in a cycad with beetle pollinator mutualists, and its ecological significance

Abstract:Cycads in the Zamiaceae are well known for their host-specific insect pollination mutualisms. Pollination of Cycas in the sister family Cycadaceae is less well-documented, with beetle pollination possibly coexisting with a limited potential for wind pollination, a hypothesis we tested for C. ophiolitica in Central Queensland, Australia. Cones were associated with three species of beetle: an undescribed weevil (Curculionidae), Hapalips sp. (Erotylidae) and Ulomoides sp. (Tenebrionidae). Pollination-vector exclusion experiments compared the pollination success (quantified as % ovules pollinated per cone) of control cones against bagged or netted cones that excluded wind or insects respectively (n = 10 for all treatments). Insects do pollinate C. ophiolitica in the absence of wind, the median (first quartile-third quartile) pollination success of control plants being 83.7% (60.8–87.2%) while bagged cones, from which wind, but not insects, were excluded, pollinated at 52.9% (19.5–74.8%). For netted cones, (excluding insects but not wind), pollination fell to 12.6% (10.9–45.9%). Airborne pollen (as quantified by capture on a series of adhesive pollen traps) decreased rapidly with distance from male cones, potentially becoming ineffective for wind pollination at ~5 m. Airborne pollen load in the vicinity of female cones, and distance of females from neighbouring males, suggests wind pollination may occur sporadically, but only at high spatial densities. Although Cycas appears to be primarily insect pollinated, this limited potential for ambophily may be significant given the history of dispersal and pollinator host shifts among these cycads.

Phytochemical study on the leaves of Wollemia nobilis

In this work, a phytochemical study performed on the leaves of the rare species, Wollemia nobilis W.G. Jones, K.D. Hill & J.M. Allen, is reported. By means of classical column chromatography and NMR Spectroscopy and Mass Spectrometry, nine compounds were evidenced. These were: pheophorbide a (1), isocupressic acid (2), acetyl-isocupressic acid (3), sandaracopimaric acid (4), agathic acid (5), 7–4′-4‴-tri-O-methyl-agathisflavone (6), 7–4′-7″-4‴-tetra-O-methyl-agathisflavone (7), caffeic acid (8) and shikimic acid (9). Compared to our previous phytochemical analysis on the male cones, some further compounds were identified i.e. compounds 1, 5, 6, 7 and 8. This confirmed the previous chemotaxonomic considerations of the species but also added new ones which were discussed within the text. In addition, a possible different accumulation of secondary metabolites in the tissues and organs of this plant was even noticed.

Pollination of the cycad Zamia incognita A. Lindstr. &amp; Idárraga by Pharaxonotha beetles in the Magdalena Medio Valley, Colombia: a mutualism dependent on a specific pollinator and its significance for conservation

The genus Zamia (Zamiaceae: Cycadales) exhibits its greatest diversity in Colombia and is highly threatened by habitat loss, extraction for ornamental plant trade, and mining, among other factors. One of the most important considerations for the effective conservation of Zamia is its highly specialized reproductive biology. Despite the importance of pollination for the populations’ viability, no studies have examined the pollination process of cycads in Colombia. Herein, we describe the pollination process of Zamia incognita A. Lindstr. & Idarraga, in a natural population. Exclusion experiments were performed by selectively excluding wind, beetles, both, or neither, which demonstrated that Pharaxonotha beetles are effective pollinators of Zamia incognita and that wind does not play any role as pollen vector. By following beetles marked with fluorescent dyes and directly observing beetle movements on and into female cones and micropyles, we confirmed that Pharaxonotha sp. is the effective pollinator of Z. incognita. The beetles traveled a maximum dispersal distance from a male to female cone of nearly 22 m and a minimum distance of 5 m. We found Pharaxonotha beetles in male cones, where they complete their life cycle. Cones produce heat in a circadian pattern associated with the elongation of the cones and pollen shedding. The increase in cones’ temperature appears to play an important role in beetle attraction. We suggest that pollination droplets on the micropyles would be a reward to pollinators. We also discuss the relationship of this Zamia species with other insects, which have important consequences for the conservation of web interactions.

Terpenoids and More Polar Compounds from the Male Cones of Wollemia nobilis.

The analysis of metabolites contained in the male cones of Wollemia nobilis was investigated for the first time in this study. Several diterpenoids of chemosystematic relevance were recognized for the first time from the genus and/or from the Araucariaceae family, namely isocupressic acid (1), acetyl-isocupressic acid (2), methyl (E)-communate (3) and sandaracopimaric acid (4). All these terpenoids are also endowed with interesting biological activities and may play a primary role in the self defence toward herbivores. The presence of a new norlabdane (norlabda-8(16)-12-dien-14,17-diol) trivially named as wollemol (5) was also recognized. Norditerpenes are scarcely distributed in Plant Kingdom and in particular in Gymnosperms and this aspect was discussed. The structure of 5 was determined by extensive NMR analysis employing mono- and bidimensional experiments. The 7-4‴-dimethoxyagathisflavone (6), a biflavonoid already recognized in Araucariaceae and W. nobilis, was also isolated from male cones together with shikimic acid (7), a biogenetic precursor of polyphenolic compounds, besides carbohydrates such as glucose (8) and saccharose (9), and arginine (10) a quite common amino acid.

A New Species ofGinkgowith Male Cones and Pollen Grains in situ from the Middle Jurassic of Eastern Xinjiang, China

Well-preserved Ginkgo pollen organs are analyzed from the Middle Jurassic Xishanyao Formation of the Turpan-Hami Basin, Xinjiang Uygur Autonomous Region, northwestern China, and are described as a new species, Ginkgo hamiensis Z.X. Wang et B.N. Sun sp. nov. The immature male cones are cylindrical and catkin-like, with two longitudinal stripes on the stalk. The pollen sacs are shaped like a long oval with two pollen sacs fused together for each microsporophyll, and the microsporophyll tip is a triangular cystidium. The pollen grains are oblong or fusiform and monocolpate; both ends are blunt or sharp. By comparison with previously reported fossil records of Ginkgo plants, we determined that the current fossils are different from all other reported species; thus, the present fossil is referred to as a new species of Ginkgo. The reproductive organs of the Ginkgo fossils described herein can provide valuable information for the study of Ginkgo plants. Further, there are two probable evolutionary trends in the Ginkgo pollen cones. One trend is that the number of pollen sacs changed from three or four during the Jurassic and Cretaceous to two at the present day; the other is that the number of pollen sacs has remained two from the Middle Jurassic to the present day. In addition, the pollen cones described herein are similar to the pollen cones of the extant Ginkgo, which strongly indicates that the morphology of Ginkgo plants may have remained highly conserved over millions of years.

Pinus remains from the Pitsidia plant assemblage document coastal pine forests in southern Crete during the late Miocene

The fossil remains of the genus Pinus are common in the European Paleogene and Neogene record. Apart from seed cones, most of the vegetative remains are difficult or even impossible to accurately classify in the modern systematic schemes of the genus. In the late Miocene assemblage of Pitsidia (Messara Basin, southern Crete) Pinus and Myrica remains dominate with thousands of vegetative and fertile specimens. The outcrop comprises a 4.5 to 5.0m thick sequence of silts and sands, rich in plant fossils. The exceptional preservation of some specimens provides significant micro-morphological and anatomical details of taxonomic value. The Pitsidia pine remains include dwarf shoots, long shoots, isolated needles, fascicle bracts, bud scales, male cones, isolated scales of male cones, seeds and ovulate cone scales. We were able to classify the material to at least subgenus and in some cases section. Both subgenera Pinus and Strobus occur in the assemblage. Concerning the dwarf shoots, three different pine species were identified, Pinus sp. – two-needled fascicles (subgen. Pinus), Pinus sp. – five-needled fascicles (subgen. Strobus) and the proposed new species Pinus pitsidiensis (subgen. Pinus) for the abundant three-needled fascicles. Lastly, we reconstruct the whole plant of P. pitsidiensis sp. nov. and discuss its paleoecology.

Actinobacteria possessing antimicrobial and antioxidant activities isolated from the pollen of scots pine (Pinus sylvestris) grown on the Baikal shore.

Isolated ecosystems existing under specific environmental conditions have been shown to be promising sources of new strains of actinobacteria. The taiga forest of Baikal Siberia has not been well studied, and its actinobacterial population remains uncharacterized. The proximity between the huge water mass of Lake Baikal and high mountain ranges influences the structure and diversity of the plant world in Siberia. Here, we report the isolation of eighteen actinobacterial strains from male cones of Scots pine trees (Pinus sylvestris) growing on the shore of the ancient Lake Baikal in Siberia. In addition to more common representative strains of Streptomyces, several species belonging to the genera Rhodococcus, Amycolatopsis, and Micromonospora were isolated. All isolated strains exhibited antibacterial and antifungal activities. We identified several strains that inhibited the growth of the pathogen Candida albicans but did not hinder the growth of Saccharomyces cerevisiae. Several isolates were active against Gram-positive and Gram-negative bacteria. The high proportion of biologically active strains producing antibacterial and specific antifungal compounds may reflect their role in protecting pollen against phytopathogens.

The ecological status of juniper woodlands in Al Jabal Al Akhdar, northern mountains of Oman

There are changes in the local distribution of the juniper, Juniperus seravschanica woodlands as a result of conflicts between biodiversity conservation and human activities in Al Jabal Al Akhdar, Sultanate of Oman. Woodland degradation and poor regeneration of juniper trees are attributed to many factors. Four zones, each with 10 plots and each plot with an area of 10,000 sq m were studied in detail at different altitudes to evaluate the status of the juniper woodlands. Tree density, distribution, health status and seed germination were assessed. The stock density of J. seravschanica in the study localities was less when compared to the previous studies. Juniper appeared as continuous woodlands from Al Hajmata reservoir in Shanut at an altitude of 2168 m a.s.l. and continued with the increase in altitude. The population structures of J. seravschanica in the four zones were evaluated. The heights of trees were normally distributed in the four zones. There were significant differences in the heights of trees among the four zones. Trees in zone 1 were shorter than those in the in the other three zones. J. seravschanica trees are in good health condition in all four zones. Most produced a moderate amount of female and male cones. Regeneration is low as indicated by 65 seedlings (9%) recorded during the survey and 26 small young trees (14%). Seed germination was low with a maximum of 31%.

Supplementary description of Cycas hongheensis (Cycadaceae) from Yunnan, China and its phylogenetic position

Cycas hongheensis was firstly proposed as a distinct taxon in 1994 and formally described two years later based on vegetative materials only. Here, the reproductive organs of this species, namely, the female cone, male cone and seeds are supplemented for description as these fertile materials were found for the first time at the type locality. Furthermore, the phylogenetic position of this species as being the only endemic member of Cycas sect. Indosinenses in China was investigated. The conflicting phylogenic results between chloroplastic (cpDNA) and nuclear DNA (nDNA) are corresponded with the inconformity characters of morphology of this species. The characters of lacking indumentum on ovules and the distinct apical spine of megasporophyll are corresponding to nDNA result while the characters such as the soft and rudimentary apical spine of the microsporophyll and the absence of fibrous layer inside the sarcotesta comform to cpDNA result. For the taxonomy, we agree this species to be classified into Cycas sect. Indosinenses for the obvious morphological characters of megasporophyll and ovule as well as deeper evidence from phylogeny based on nuclear data, as biparental inherited nuclear genes could offer more comprehensive genetic information than maternal inherited cpDNA.

Inferring the chemical form of 137Cs deposited by the Fukushima Dai-ichi Nuclear Power Plant accident by measuring 137Cs incorporated into needle leaves and male cones of Japanese cedar trees

We hypothesized that the water-soluble (ionic) and water-insoluble (stable) radiocesium from the initial fallout of the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident was distributed in various proportions in the surrounding areas and that this distribution was reflected in the trees that suffered deposition from the initial fallout. This study attempted to evaluate local variations in the chemical form of 137Cs derived from the initial fallout of the FDNPP accident and whether its chemical form affected the radiocesium concentration in the tissues currently growing in trees, even after the initial fallout ceased. For these estimations, the ratio between the 137Cs concentration in Cryptomeria japonica needle leaves in the tree crown, which existed before the FDNPP accident and subsequently directly exposed to the initial fallout (137Cspre-accident N), and the amount of 137Cs in the initial fallout itself (137Csfallout) was determined (137Cspre-accident N/137Csfallout) at 66 sites. In addition, the 137Cs ratios between the male cones produced in 2012 (137Csmale cone) and needle leaves that had elongated in the spring of 2011 (137Cs2011N) was determined at 82 sites (137Csmale cone/137 Cs2011N). Most of the sites with lower 137Cspre-accident N/137Csfallout ratios were distributed in eastern Fukushima, relatively close to the Pacific Ocean coastline. Lower 137Cspre-accidentN/137Csfallout and higher 137Csmalecone/137Cs2011N were found to be associated with higher proportions of 137Cs in ionic forms. These observations are consistent with the hypothesis, and likely reflect regional variations in the chemical form of the deposited radiocesium.

Reproductive morphology in the Gnetum cuspidatum group (Gnetales) and its implications for pollination biology in the Gnetales

Background and aims – The Gnetales include the extant genera Gnetum, Ephedra and Welwitschia . They are usually functionally dioecious, but male cones often have sterile (but pollination drop-producing) ovules in addition to male units. There are, however, exceptions, i.e. most species of Ephedra and African species of Gnetum . Furthermore, the literature contains conflicting information on the Asian Gnetum cuspidatum . One study states that sterile ovules are present in this species; another that they are absent. The latter also claims that male cones secrete nectar instead, which is interesting because nectar has only been suggested to be present in four gymnosperm species. Here we aim to elucidate whether or not sterile ovules are present in male cones of G. cuspidatum and related taxa, evaluate evidence for nectar being present in gymnosperms and discuss implications for pollination biology. Methods – Male cones from relevant taxa were examined using a dissecting microscope and scanning electron microscopy. Key results – Sterile ovules are present in G. cuspidatum and the related G. macrostachyum, G. microcarpum, G. diminutum and G. loerzingii, but they are minute, hidden among hairs, and easily overlooked. No indications of nectar or nectaries were found and their presence in Asian species of Gnetum is questioned. Conclusions – Insect pollination is probably ancestral in the Gnetales. Like most species of Gnetum, members of the G. cuspidatum group have sterile ovules in male cones, and they can thus attract pollinators to both male and female plants using sweet pollination drops. Although it is possible that these species, in addition, produce extraovular reward for pollinators, we find no such evidence. Instead, it seems plausible that pollination drops have been mistaken for (extraovular) nectar. However, African species of Gnetum have unisexual male cones. Have they developed another means of pollinator reward in male plants or are they wind-pollinated as are their ephedran analogues?

A transcriptomics investigation into pine reproductive organ development.

The development of reproductive structures in gymnosperms is still poorly studied because of a lack of genomic information and useful genetic tools. The hermaphroditic reproductive structure derived from unisexual gymnosperms is an even less studied aspect of seed plant evolution. To extend our understanding of the molecular mechanism of hermaphroditism and the determination of sexual identity of conifer reproductive structures in general, unisexual and bisexual cones from Pinus tabuliformis were profiled for gene expression using 60K microarrays. Expression patterns of genes during progression of sexual cone development were analysed using RNA-seq. The results showed that, overall, the transcriptomes of male structures in bisexual cones were more similar to those of female cones. However, the expression of several MADS-box genes in the bisexual cones was similar to that of male cones at the more juvenile developmental stage, while despite these expression shifts, male structures of bisexual cones and normal male cones were histologically indistinguishable and cone development was continuous. This study represents a starting point for in-depth analysis of the molecular regulation of cone development and also the origin of hermaphroditism in pine.

Identification and expression profiles of sRNAs and their biogenesis and action-related genes in male and female cones of Pinus tabuliformis.

BackgroundSmall RNA (sRNA) play pivotal roles in reproductive development, and their biogenesis and action mechanisms are well characterised in angiosperm plants; however, corresponding studies in conifers are very limited. To improve our understanding of the roles of sRNA pathways in the reproductive development of conifers, the genes associated with sRNA biogenesis and action pathways were identified and analysed, and sRNA sequencing and parallel analysis of RNA ends (PARE) were performed in male and female cones of the Chinese pine (Pinus tabuliformis).ResultsBased on high-quality reference transcriptomic sequences, 21 high-confidence homologues involved in sRNA biogenesis and action in P. tabuliformis were identified, including two different DCL3 genes and one AGO4 gene. More than 75 % of genes involved in sRNA biogenesis and action have higher expression levels in female than in male cones. Twenty-six microRNA (miRNA) families and 74 targets, including 46 24-nt sRNAs with a 5’ A, which are specifically expressed in male cones or female cones and probably bind to AGO4, were identified.ConclusionsThe sRNA pathways have higher activity in female than in male cones, and the miRNA pathways are the main sRNA pathways in P. tabuliformis. The low level of 24-nt short-interfering RNAs in conifers is not caused by the absence of biogenesis-related genes or AGO-binding proteins, but most likely caused by the low accumulation of these key components. The identification of sRNAs and their targets, as well as genes associated with sRNA biogenesis and action, will provide a good starting point for investigations into the roles of sRNA pathways in cone development in conifers.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-1885-6) contains supplementary material, which is available to authorized users.

Study of the Histology of Leafy Axes and Male Cones of Glenrosa carentonensis sp. nov. (Cenomanian Flints of Charente-Maritime, France) Using Synchrotron Microtomography Linked with Palaeoecology

We report exceptionally well-preserved plant remains ascribed to the extinct conifer Glenrosa J. Watson et H.L. Fisher emend. V. Srinivasan inside silica-rich nodules from the Cenomanian of the Font-de-Benon quarry, Charente-Maritime, western France. Remains are preserved in three dimensions and mainly consist of fragmented leafy axes. Pollen cones of this conifer are for the first time reported and in some cases remain connected to leafy stems. Histology of Glenrosa has not previously been observed; here, most of internal tissues and cells are well-preserved and allow us to describe a new species, Glenrosa carentonensis sp. nov., using propagation phase-contrast X-ray synchrotron microtomography, a non-destructive technique. Leafy axes consist of characteristic helically arranged leaves bearing stomatal crypts. Glenrosa carentonensis sp. nov. differs from the other described species in developing a phyllotaxy 8/21, claw-shaped leaves, a thicker cuticle, a higher number of papillae and stomata per crypt. Pollen cones consist of peltate, helically arranged microsporophylls, each of them bearing 6–7 pollen sacs. The new high resolution tomographic approach tested here allows virtual palaeohistology on plants included inside a dense rock to be made. Most tissues of Glenrosa carentonensis sp. nov. are described. Lithological and palaeontological data combined with xerophytic features of Glenrosa carentonensis sp. nov. suggest that this conifer has been adapted to survive in harsh and instable environments such as coastal area exposed to hot, dry conditions.

Digital gene expression analysis of male and female bud transition in Metasequoia reveals high activity of MADS-box transcription factors and hormone-mediated sugar pathways.

Metasequoia glyptostroboides is a famous redwood tree of ecological and economic importance, and requires more than 20 years of juvenile-to-adult transition before producing female and male cones. Previously, we induced reproductive buds using a hormone solution in juvenile Metasequoia trees as young as 5-to-7 years old. In the current study, hormone-treated shoots found in female and male buds were used to identify candidate genes involved in reproductive bud transition in Metasequoia. Samples from hormone-treated cone reproductive shoots and naturally occurring non-cone setting shoots were analyzed using 24 digital gene expression (DGE) tag profiles using Illumina, generating a total of 69,520 putative transcripts. Next, 32 differentially and specifically expressed transcripts were determined using quantitative real-time polymerase chain reaction, including the upregulation of MADS-box transcription factors involved in male bud transition and flowering time control proteins involved in female bud transition. These differentially expressed transcripts were associated with 243 KEGG pathways. Among the significantly changed pathways, sugar pathways were mediated by hormone signals during the vegetative-to-reproductive phase transition, including glycolysis/gluconeogenesis and sucrose and starch metabolism pathways. Key enzymes were identified in these pathways, including alcohol dehydrogenase (NAD) and glutathione dehydrogenase for the glycolysis/gluconeogenesis pathway, and glucanphosphorylase for sucrose and starch metabolism pathways. Our results increase our understanding of the reproductive bud transition in gymnosperms. In addition, these studies on hormone-mediated sugar pathways increase our understanding of the relationship between sugar and hormone signaling during female and male bud initiation in Metasequoia.