Search

Floral transition is a critical and strictly regulated developmental process in plants. Mutations in Arabidopsis LIKE HETEROCHROMATIN PROTEIN 1 (AtLHP1)/TERMINAL FLOWER 2 (TFL2) result in early and terminal flowers. Little is known about the gene expression, function and evolution of plant LHP1 homologs, except for Arabidopsis LHP1. In this study, the conservation and divergence of plant LHP1 protein sequences was analyzed by sequence alignments and phylogeny. LHP1 expression patterns were compared among taxa that occupy pivotal phylogenetic positions. Several relatively conserved new motifs/regions were identified among LHP1 homologs. Phylogeny of plant LHP1 proteins agreed with established angiosperm relationships. In situ hybridization unveiled conserved expression of plant LHP1 in the axillary bud/tiller, vascular bundles, developing stamens, and carpels. Unlike AtLHP1, cucumber CsLHP1-2, sugarcane SoLHP1 and maize ZmLHP1, rice OsLHP1 is not expressed in the shoot apical meristem (SAM) and the OsLHP1 transcript level is consistently low in shoots. "Unequal crossover" might have contributed to the divergence in the N-terminal and hinge region lengths of LHP1 homologs. We propose an "insertion-deletion" model for soybean (Glycine max L.) GmLHP1s evolution. Plant LHP1 homologs are more conserved than previously expected, and may favor vegetative meristem identity and primordia formation. OsLHP1 may not function in rice SAM during floral induction.

Summary In flowering plants, the anther contains highly specialized reproductive and somatic cells that are required for male fertility. Genetic studies have uncovered several genes that are important for anther development. However, little information is available regarding most genes active during anther development, including possible relationships between these genes and genetically defined regulators. In Arabidopsis, two previously isolated male-sterile mutants display dramatically altered anther cell differentiation patterns. The sporocyteless (spl)/nozzle (nzz) mutant is defective in the differentiation of primary sporogenous cells into microsporocytes, and does not properly form the anther wall. The excess microsporocytes1 (ems1)/extrasporogenous cells (exs) mutants produce excess microsporocytes at the expense of the tapetum. To gain additional insights into microsporocyte and tapetum differentiation and to uncover potential genetic interactions, expression profiles were compared between wild-type anthers (stage 4–6) and those of the spl or ems1 mutants. A total of 1954 genes were found to be differentially expressed in the ems1 and/or spl anthers, and these were grouped into 14 co-expression clusters. The presence of genes with known and predicted functions in specific clusters suggests potential functions for other genes in the same cluster. To obtain clues about possible co-regulation within co-expression clusters, we searched for shared cis-regulatory motifs in putative promoter regions. Our analyses were combined with data from previous studies to develop a model of the anther gene regulatory network. This model includes hypotheses that can be tested experimentally to gain further understanding of the mechanisms controlling anther development.

A floral developmental series was determined for Persea americana (Lauraceae, avocado), and the floral morphology of this species was compared with available data for other members of Persea. We compared the structure of the inflorescence and flower with that of vegetative shoots with respect to phyllotaxy and leaf shape. The inflorescence is a determinate thyrse (panicle) with variable numbers of lateral branches. Staminal glands in Persea may represent abaxial‐marginal emergences rather than stamens. However, these glands are occasionally involved in transitions to pollen sacs and ovary margins. Stigmas, pollen sacs, staminal appendages, glands of staminodes, and margins of tepals share features that are subjectively associated with “androecia.” In the innermost androecial whorl, staminodial glands appear united because of the reduction of the middle portion to a staminodial apex. The apex of staminodes is homologous to the filament and anther, as well as to the stigma of the carpel, and corresponds to ...

Congenital penile anomalies (CPAs) are among the most common human birth defects. Reports of CPAs, which include hypospadias, chordee, micropenis, and ambiguous genitalia, have risen sharply in recent decades, but the causes of these malformations are rarely identified. Both genetic anomalies and environmental factors, such as antiandrogenic and estrogenic endocrine disrupting chemicals (EDCs), are suspected to cause CPAs; however, little is known about the temporal window(s) of sensitivity to EDCs, or the tissue-specific roles and downstream targets of the androgen receptor (AR) in external genitalia. Here, we show that the full spectrum of CPAs can be produced by disrupting AR at different developmental stages and in specific cell types in the mouse genital tubercle. Inactivation of AR during a narrow window of prenatal development results in hypospadias and chordee, whereas earlier disruptions cause ambiguous genitalia and later disruptions cause micropenis. The neonatal phase of penile development is controlled by the balance of AR to estrogen receptor α (ERα) activity; either inhibition of androgen or augmentation of estrogen signaling can induce micropenis. AR and ERα have opposite effects on cell division, apoptosis, and regulation of Hedgehog, fibroblast growth factor, bone morphogenetic protein, and Wnt signaling in the genital tubercle. We identify Indian hedgehog (Ihh) as a novel downstream target of AR in external genitalia and show that conditional deletion of Ihh inhibits penile masculinization. These studies reveal previously unidentified cellular and molecular mechanisms by which antiandrogenic and estrogenic signals induce penile malformations and demonstrate that the timing of endocrine disruption can determine the type of CPA.

The perianth of Persea americana (Lauraceae) consists of two whorls of morphologically similar laminar organs, termed tepals. Closely related Persea borbonia, however, produces a dimorphic perianth with smaller outer tepals. To assess whether homologues of floral organ identity genes in Persea may play a role in shaping this dimorphic perianth, we compared their expression patterns in the two species. A homologue of AP1 (A‐function) is expressed at low levels in both perianth types but was not tepal specific. Homologues of AGL6, however, show the tepal‐specific expression pattern expected of A‐function genes. Homologues of AP3 and PI (B‐function) are expressed in tepals of both perianth types, indicating that perianth dimorphism in Persea is not regulated by these genes. Differential expression across the dimorphic perianth as absence late in outer tepal development was evident for homologues of AG (C‐function) and SEP3 (E‐function). Genetic studies in model systems indicate a conserved role for AG homolo...

The aqueous extracts of 24 herbs traditionally used as curing ischemic heart disease in clinic in China were screened for their in vitro angiogenic activity, another twenty-four traditionally used as anti-tumor or anti-inflammatory remedies in China were screened for their in vitro anti-angiogenic activity. The activity of angiogenesis was determined by quantitation of vessels on chick embryo chorioallantoic membrane (CAM) model and cell proliferation of cultured bovine aortic endothelial cells (BAECs). Among the herbal extracts examined, the aqueous extracts of Epimedium sagittatum, Trichosanthes kirilowii and Dalbergia odorifera showed the strong angiogenetic activity both in CAM and BAECs models; and the aqueous extracts of Berberis paraspecta, Catharanthus roseus, Coptis chinensis, Taxus chinensis, Scutellaria baicalensis, Polygonum cuspidatum and Scrophularia ningpoensis elicited significant inhibition at a concentration of 1g dry herb /ml.

We investigated the effect of cadmium (Cd) on the yield of ajmalicine, a secondary metabolite derived from tryptophan, in the suspension cultures of a fully habituated cell line of Catharanthus roseus. The treatment with Cd concentration ranging from 0.05 to 0.4 mM and the duration of 24 to 48 h increased ajmalicine production and excretion into culture medium, particularly for cells at the mid-exponential growth phase. For early stationary phase cells and stationary phase cells transferred from the culturing medium to the production medium, we detected less enhancement. Cd treatment in cells at the mid-exponential phase, early stationary phase, and cells transferred from the growth medium to production medium increased the cellular content of tryptophan and tryptamine, the precursors for ajmalicine. The tryptamine level was a major limiting factor for ajmalicine production for cells at the mid-exponential phase. The tryptophan decarboxylase (TDC) converting tryptophan to tryptamine was also affected by Cd. We demonstrated that Cd treatment increased the level of TDC transcript, the cellular tryptamine concentration, and ajmalicine excretion, all contributed to the higher yield of ajmalicine. The increase was more significant in cells with active metabolic status and the cellular tryptamine concentration was the major limiting factor for ajmalicine biosynthesis.

The evolutionary success of mammals is rooted in their high metabolic rate. A high metabolic rate is sustainable thanks to efficient food processing and that in turn is facilitated by precise occlusion of the teeth and the acquisition of rhythmic mastication. These major evolutionary innovations characterize most members of the Class Mammalia. Cetaceans are one of the few groups of mammals in which precise occlusion has been secondarily lost. Most toothed whales have an increased number of simple crowned teeth that are similar along the tooth row. Evolution toward these specializations began immediately after the time cetaceans transitioned from terrestrial-to-marine environments. The fossil record documents the critical aspects of occlusal evolution of cetaceans, and allows us to pinpoint the evolutionary timing of the macroevolutionary events leading to their unusual dental morphology among mammals. The developmental controls of tooth differentiation and tooth number have been studied in a few mammalian clades, but nothing is known about how these controls differ between cetaceans and mammals that retain functional occlusion. Here we show that pigs, a cetacean relative with regionalized tooth morphology and complex tooth crowns, retain the typical mammalian gene expression patterns that control early tooth differentiation, expressing Bmp4 in the rostral (mesial, anterior) domain of the jaw, and Fgf8 caudally (distal, posterior). By contrast, dolphins have lost these regional differences in dental morphology and the Bmp4 domain is extended into the caudal region of the developing jaw. We hypothesize that the functional constraints underlying mammalian occlusion have been released in cetaceans, facilitating changes in the genetic control of early dental development. Such major developmental changes drive morphological evolution and are correlated with major shifts in diet and food processing during cetacean evolution.

Mediator is a conserved multi-protein complex that plays an important role in regulating transcription by mediating interactions between transcriptional activator proteins and RNA polymerase II. Much evidence exists that Mediator plays a constitutive role in the transcription of all genes transcribed by RNA polymerase II. However, evidence is mounting that specific Mediator subunits may control the developmental regulation of specific subsets of RNA polymerase II-dependent genes. Although the Mediator complex has been extensively studied in yeast and mammals, only a few reports on Mediator function in flowering time control of plants, little is known about Mediator function in floral organ identity. Here we show that in Arabidopsis thaliana, MEDIATOR SUBUNIT 18 (MED18) affects flowering time and floral organ formation through FLOWERING LOCUS C (FLC) and AGAMOUS (AG). A MED18 loss-of-function mutant showed a remarkable syndrome of later flowering and altered floral organ number. We show that FLC and AG mRNA levels and AG expression patterns are altered in the mutant. Our results support parallels between the regulation of FLC and AG and demonstrate a developmental role for Mediator in plants.

Huang Qin (root of Scutellaria baicalensis) is a widely used herb in different countries for adjuvant therapy of inflammation, diabetes, hypertension, different kinds of cancer and virus related diseases. Baicalin is the main flavonoid in this herb and has been extensively studied for 30 years. The angiogenic effect of herb Huang Qin extract and baicalin was found 13 years ago, however, the results were controversial with pro-angiogenic effect in some studies and anti-angiogenic effect in others. In this paper, the angiogenic effect of baicalin, its aglycone form baicalein and aqueous extract of Huang Qin was studied in chick embryo chorioallantoic membrane (CAM) model. Dose dependent dual effect was found in both aqueous extract and baicalin, but not in baicalein, in which only inhibitory effect was observed. In order to reveal the cellular and molecular mechanism of how baicalin and baicalein affect angiogenesis, cell proliferation and programmed cell death assays were performed in treated CAM. In addition, quantitative PCR array including 84 angiogenesis related genes was used to detect high and low dosage of baicalin and baicalein responsive genes. Low dose baicalin increased cell proliferation in developing blood vessels through upregulation of multiple angiogenic genes expression, but high dose baicalin induced cell death, performing inhibitory effect on angiogenesis. Both high and low dose of baicalein down regulated the expression of multiple angiogenic genes, decreased cell proliferation, and leads to inhibitory effects on angiogenesis.

Recessive mutations in the SIAMESE (SIM) gene of Arabidopsis thaliana result in multicellular trichomes harboring individual nuclei with a low ploidy level, a phenotype strikingly different from that of wild-type trichomes, which are single cells with a nuclear DNA content of ∼16C to 32C. These observations suggested that SIM is required to suppress mitosis as part of the switch to endoreplication in trichomes. Here, we demonstrate that SIM encodes a nuclear-localized 14-kD protein containing a cyclin binding motif and a motif found in ICK/KRP (for Interactors of Cdc2 kinase/Kip-related protein) cell cycle inhibitor proteins. Accordingly, SIM was found to associate with D-type cyclins and CDKA;1. Homologs of SIM were detected in other dicots and in monocots but not in mammals or fungi. SIM proteins are expressed throughout the shoot apical meristem, in leaf primordia, and in the elongation zone of the root and are localized to the nucleus. Plants overexpressing SIM are slow-growing and have narrow leaves and enlarged epidermal cells with an increased DNA content resulting from additional endocycles. We hypothesize that SIM encodes a plant-specific CDK inhibitor with a key function in the mitosis-to-endoreplication transition.

The functional diversification of duplicated genes is one of the driving forces in evolution. To understand the molecular mechanisms of gene diversification, we studied the functional relationship of the two Arabidopsis paralogous MYB-related genes GL1 and MYB23. We show that MYB23 controls trichome branching and trichome initiation at leaf edges. The latter is controlled redundantly together with GL1. We show that the two proteins are functionally equivalent during trichome initiation but not during trichome branching. RT-PCR and reporter construct analysis revealed spatial, temporal and genetic differences in transcriptional regulation of the GL1 and MYB23 genes. Presented data indicate that the diversification of GL1 and MYB23 gene functions occurred at the level of cis-regulatory sequences with respect to trichome initiation, and that, in parallel, the diversification with respect to regulation of trichome branching also involved changes in respective proteins.

The PRETTY FEW SEEDS2 gene encodes a homeodomain protein that regulates ovule development. In peptide alignments spanning the homeodomain and the WOX domain, PFS2 shared 95% amino acid identity with the PRESSED FLOWER and WUSCHEL proteins. In the pfs2-1 allele, the integuments display morphological abnormalities and 95% of the embryo sacs fail to develop properly, which results in reduced fecundity. PFS2 transcripts were most abundant in developing ovules, which accounts for the ovule phenotype in pfs2 mutants. In addition, PFS2 transcripts were present in developing primordia and differentiating organs, but, interestingly, they were absent during cell maturation. Ectopic PFS2 expression interfered with differentiation of primordia from meristems. For most plants, this resulted in fasciated stems, altered phyllotaxy, a cessation of primordia differentiation, or a combination of these. In the plants that made ovules,ectopic PFS2 expression blocked megaspore mother cell differentiation and often impeded polarized growth of the outer integument. PFS2 activity altered AGAMOUS expression, which accounts for some of the gain- and loss-of-function phenotypes. Based on analyses presented here, PFS2 affects either ovule patterning or differentiation.