DWARF27 and CAROTENOID CLEAVAGE DIOXYGENASE 7 genes regulate release, germination and growth of gemma in Marchantia polymorpha.

Strigolactones (SLs), a class of carotenoid-derived hormones, play a crucial role in flowering plants by regulating underground communication with symbiotic arbuscular mycorrhizal fungi (AM) and controlling shoot and root architecture. While the functions of core SL genes have been characterized in many plants, their roles in non-tracheophyte plants like liverworts require further investigation. In this study, we employed the model liverwort species Marchantia polymorpha, which lacks detectable SL production and orthologs of key SL biosynthetic genes, including CAROTENOID CLEAVAGE DIOXYGENASE 8 (CCD8) and MORE AXILLARY GROWTH 1 (MAX1). However, it retains some SL pathway components, including DWARF27 (D27) and CCD7. To help elucidate the function of these remaining components in M. polymorpha, knockout mutants were generated for MpD27-1, MpD27-2 and MpCCD7. Phenotypic comparisons of these mutants with the wild-type control revealed a novel role for these genes in regulating the release of gemmae from the gemma cup and the germination and growth of gemmae in the dark. Mpd27-1, Mpd27-2, and Mpccd7 mutants showed lower transcript abundance of genes involved in photosynthesis, such as EARLY LIGHT INDUCED (ELI), and stress responses such as LATE EMBRYOGENESIS ABUNDANT (LEA) but exhibited higher transcript levels of ETHYLENE RESPONSE FACTORS (ERFs) and SL and carotenoid related genes, such as TERPENE SYNTHASE (TS), CCD7 and LECITHIN-RETINAL ACYL TRANSFERASE (LRAT). Furthermore, the mutants of M. polymorpha in the SL pathway exhibited increased contents of carotenoid. This unveils a previously unrecognized role for MpD27-1, MpD27-2 and MpCCD7 in controlling release, germination, and growth of gemmae in response to varying light conditions. These discoveries enhance our comprehension of the regulatory functions of SL biosynthesis genes in non-flowering plants.

Painted flowers: Eluta generates pigment patterning in Antirrhinum.

In the early 1900s, Erwin Baur established Antirrhinum majus as a model system, identifying and characterising numerous flower colour variants. This included Picturatum/Eluta, which restricts the accumulation of magenta anthocyanin pigments, forming bullseye markings on the flower face. We identified the gene underlying the Eluta locus by transposon-tagging, using an Antirrhinum line that spontaneously lost the nonsuppressive el phenotype. A candidate MYB repressor gene at this locus contained a CACTA transposable element. We subsequently identified plants where this element excised, reverting to a suppressive Eluta phenotype. El alleles inhibit expression of anthocyanin biosynthetic genes, confirming it to be a regulatory locus. The modes of action of Eluta were investigated by generating stable transgenic tobacco lines, biolistic transformation of Antirrhinum petals and promoter activation/repression assays. Eluta competes with MYB activators for promoter cis-elements, and also by titrating essential cofactors (bHLH proteins) to reduce transcription of target genes. Eluta restricts the pigmentation established by the R2R3-MYB factors, Rosea and Venosa, with the greatest repression on those parts of the petals where Eluta is most highly expressed. Baur questioned the origin of heredity units determining flower colour variation in cultivated A. majus. Our findings support introgression from wild species into cultivated varieties.

Production of Betacyanins in Transgenic Nicotiana tabacum Increases Tolerance to Salinity.

Although red betalain pigments (betacyanins) have been associated with salinity tolerance in some halophytes like Disphyma australe, efforts to determine whether they have a causal role and the underlying mechanisms have been hampered by a lack of a model system. To address this, we engineered betalain-producing Nicotiana tabacum, by the introduction of three betalain biosynthetic genes. The plants were violet-red due to the accumulation of three betacyanins: betanin, isobetanin, and betanidin. Under salt stress, betacyanic seedlings had increased survivability and leaves of mature plants had higher photochemical quantum yields of photosystem II (F v /F m ) and faster photosynthetic recovery after saturating light treatment. Under salt stress, compared to controls betacyanic leaf disks had no loss of carotenoids, a slower rate of chlorophyll degradation, and higher F v /F m values. Furthermore, simulation of betacyanin pigmentation by using a red filter cover improved F v /F m value of green tissue under salt stress. Our results confirm a direct causal role of betacyanins in plant salinity tolerance and indicate a key mechanism is photoprotection. A role in delaying leaf senescence was also indicated, and the enhanced antioxidant capability of the betacyanic leaves suggested a potential contribution to scavenging reactive oxygen species. The study can inform the development of novel biotechnological approaches to improving agricultural productivity in saline-affected areas.

The Evolution of Flavonoid Biosynthesis: A Bryophyte Perspective.

The flavonoid pathway is one of the best characterized specialized metabolite pathways of plants. In angiosperms, the flavonoids have varied roles in assisting with tolerance to abiotic stress and are also key for signaling to pollinators and seed dispersal agents. The pathway is thought to be specific to land plants and to have arisen during the period of land colonization around 550-470 million years ago. In this review we consider current knowledge of the flavonoid pathway in the bryophytes, consisting of the liverworts, hornworts, and mosses. The pathway is less characterized for bryophytes than angiosperms, and the first genetic and molecular studies on bryophytes are finding both commonalities and significant differences in flavonoid biosynthesis and pathway regulation between angiosperms and bryophytes. This includes biosynthetic pathway branches specific to each plant group and the apparent complete absence of flavonoids from the hornworts.

MYBA From Blueberry (Vaccinium Section Cyanococcus) Is a Subgroup 6 Type R2R3MYB Transcription Factor That Activates Anthocyanin Production.

The Vaccinium genus in the family Ericaceae comprises many species, including the fruit-bearing blueberry, bilberry, cranberry, huckleberry, and lingonberry. Commercially, the most important are the blueberries (Vaccinium section Cyanococcus), such as Vaccinium corymbosum (northern highbush blueberry), Vaccinium virgatum (rabbiteye blueberry), and Vaccinium angustifolium (lowbush blueberry). The rising popularity of blueberries can partly be attributed to their "superfood" status, with an increasing body of evidence around human health benefits resulting from the fruit metabolites, particularly products of the phenylpropanoid pathway such as anthocyanins. Activation of anthocyanin production by R2R3-MYB transcription factors (TFs) has been characterized in many species, but despite recent studies on blueberry, cranberry, and bilberry, no MYB anthocyanin regulators have been reported for Vaccinium. Indeed, there has been conjecture that at least in bilberry, MYB TFs divergent to the usual type are involved. We report identification of MYBA from blueberry, and show through sequence analysis and functional studies that it is homologous to known anthocyanin-promoting R2R3-MYBs of subgroup 6 of the MYB superfamily. In transient assays, MYBA complemented an anthocyanin MYB mutant of Antirrhinum majus and, together with a heterologous bHLH anthocyanin regulator, activated anthocyanin production in Nicotiana benthamiana. Furthermore anthocyanin accumulation and anthocyanin structural gene expression (assayed by qPCR and RNA-seq analyses) correlated with MYBA expression, and MYBA was able to transactivate the DFR promoter from blueberry and other species. The RNA-seq data also revealed a range of other candidate genes involved in the regulation of anthocyanin production in blueberry fruit. The identification of MYBA will help to resolve the regulatory mechanism for anthocyanin pigmentation in the Vaccinium genus. The sequence information should also prove useful in developing tools for the accelerated breeding of new Vaccinium cultivars.

In the Solanaceae, a hierarchy of bHLHs confer distinct target specificity to the anthocyanin regulatory complex.

The anthocyanin biosynthetic pathway is regulated by a transcription factor complex consisting of an R2R3 MYB, a bHLH, and a WD40. Although R2R3 MYBs belonging to the anthocyanin-activating class have been identified in many plants, and their role well elucidated, the subgroups of bHLH implicated in anthocyanin regulation seem to be more complex. It is not clear whether these potential bHLH partners are biologically interchangeable with redundant functions, or even if heterodimers are involved. In this study, AcMYB110, an R2R3 MYB isolated from kiwifruit (Actinidia sp.) showing a strong activation of the anthocyanin pathway in tobacco (Nicotiana tabacum) was used to examine the function of interacting endogenous bHLH partners. Constitutive expression of AcMYB110 in tobacco leaves revealed different roles for two bHLHs, NtAN1 and NtJAF13. A hierarchical mechanism is shown to control the regulation of transcription factors and consequently of the anthocyanin biosynthetic pathway. Here, a model is proposed for the regulation of the anthocyanin pathway in Solanaceous plants in which AN1 is directly involved in the activation of the biosynthetic genes, whereas JAF13 is involved in the regulation of AN1 transcription.

A conserved network of transcriptional activators and repressors regulates anthocyanin pigmentation in eudicots.

Plants require sophisticated regulatory mechanisms to ensure the degree of anthocyanin pigmentation is appropriate to myriad developmental and environmental signals. Central to this process are the activity of MYB-bHLH-WD repeat (MBW) complexes that regulate the transcription of anthocyanin genes. In this study, the gene regulatory network that regulates anthocyanin synthesis in petunia (Petunia hybrida) has been characterized. Genetic and molecular evidence show that the R2R3-MYB, MYB27, is an anthocyanin repressor that functions as part of the MBW complex and represses transcription through its C-terminal EAR motif. MYB27 targets both the anthocyanin pathway genes and basic-helix-loop-helix (bHLH) ANTHOCYANIN1 (AN1), itself an essential component of the MBW activation complex for pigmentation. Other features of the regulatory network identified include inhibition of AN1 activity by the competitive R3-MYB repressor MYBx and the activation of AN1, MYB27, and MYBx by the MBW activation complex, providing for both reinforcement and feedback regulation. We also demonstrate the intercellular movement of the WDR protein (AN11) and R3-repressor (MYBx), which may facilitate anthocyanin pigment pattern formation. The fundamental features of this regulatory network in the Asterid model of petunia are similar to those in the Rosid model of Arabidopsis thaliana and are thus likely to be widespread in the Eudicots.

Nódulos pulmonares subsólidos en tomografía computada multicorte. Características y diagnósticos diferenciales con el adenocarcinoma de pulmón / Subsolid pulmonary nodules at multislice computed tomography. Characteristics and differential diagnosis with lung adenocarcinoma

En el último tiempo se ha incrementado la detección de nódulos pulmonares, debido al uso de la tomografía computada multicorte (TCMC) y a la implementación de métodos de cribado de cáncer de pulmón mediante el uso de la tomografía computada (TC) de baja dosis. Esto ha despertado especial interés en los nódulos de tipo subsólido por su probabilidad de tener una etiología maligna, en particular el adenocarcinoma (ADC). Con el análisis minucioso de las imágenes adquiridas en la tomografía computada multicorte se pueden identificar las características morfológicas de cada nódulo y realizar una correlación en forma aproximada con su probable anatomía patológica. La evaluación, junto con el contexto clínico-epidemiológico del paciente, hace posible un diagnóstico presuntivo y un pronóstico aproximado, permitiendo determinar las conductas terapéuticas o los planes de seguimiento...

The molecular basis for venation patterning of pigmentation and its effect on pollinator attraction in flowers of Antirrhinum.

Pigment stripes associated with veins (venation) is a common flower colour pattern. The molecular genetics and function of venation were investigated in the genus Antirrhinum, in which venation is determined by Venosa (encoding an R2R3MYB transcription factor). Pollinator preferences were measured by field tests with Antirrhinum majus. Venosa function was examined using in situ hybridization and transient overexpression. The origin of the venation trait was examined by molecular phylogenetics. Venation and full-red flower colouration provide a comparable level of advantage for pollinator attraction relative to palely pigmented or white lines. Ectopic expression of Venosa confers pigmentation outside the veins. Venosa transcript is produced only in small areas of the corolla between the veins and the adaxial epidermis. Phylogenetic analyses suggest that venation patterning is an ancestral trait in Antirrhinum. Different accessions of three species with full-red pigmentation with or without venation patterning have been found. Epidermal-specific venation is defined through overlapping expression domains of the MYB (myoblastoma) and bHLH (basic Helix-Loop-Helix) co-regulators of anthocyanin biosynthesis, with the bHLH providing epidermal specificity and Venosa vein specificity. Venation may be the ancestral trait, with full-red pigmentation a derived, polyphyletic trait. Venation patterning is probably not fixed once species evolve full-red floral pigmentation.

Methods for transient assay of gene function in floral tissues.

BACKGROUND: There is considerable interest in rapid assays or screening systems for assigning gene function. However, analysis of gene function in the flowers of some species is restricted due to the difficulty of producing stably transformed transgenic plants. As a result, experimental approaches based on transient gene expression assays are frequently used. Biolistics has long been used for transient over-expression of genes of interest, but has not been exploited for gene silencing studies. Agrobacterium-infiltration has also been used, but the focus primarily has been on the transient transformation of leaf tissue. RESULTS: Two constructs, one expressing an inverted repeat of the Antirrhinum majus (Antirrhinum) chalcone synthase gene (CHS) and the other an inverted repeat of the Antirrhinum transcription factor gene Rosea1, were shown to effectively induce CHS and Rosea1 gene silencing, respectively, when introduced biolistically into petal tissue of Antirrhinum flowers developing in vitro. A high-throughput vector expressing the Antirrhinum CHS gene attached to an inverted repeat of the nos terminator was also shown to be effective. Silencing spread systemically to create large zones of petal tissue lacking pigmentation, with transmission of the silenced state spreading both laterally within the affected epidermal cell layer and into lower cell layers, including the epidermis of the other petal surface. Transient Agrobacterium-mediated transformation of petal tissue of tobacco and petunia flowers in situ or detached was also achieved, using expression of the reporter genes GUS and GFP to visualise transgene expression. CONCLUSION: We demonstrate the feasibility of using biolistics-based transient RNAi, and transient transformation of petal tissue via Agrobacterium infiltration to study gene function in petals. We have also produced a vector for high throughput gene silencing studies, incorporating the option of using T-A cloning to insert the gene sequence of interest. These techniques should allow analysis of gene function in a much broader range of flower species.