Project description:The transition from vegetative growth to flower formation is critical for the survival of flowering plants. The plant-specific transcription factor LEAFY (LFY) has central, evolutionarily conserved roles in this process, both in the formation of the first flower and later in floral patterning. We performed genome-wide binding and expression studies to elucidate the molecular mechanisms by which LFY executes these roles. Our study reveals that LFY directs an intricate regulatory network in control of floral homeotic gene expression and, unexpectedly, controls the expression of genes regulating the response to external stimuli in Arabidopsis. We further show that LFY dampens responses to a bacterial MAMP (microbe-associated molecular pattern) and to pathogen challenge. Our findings suggest a molecular mechanism for the coordination of reproductive stage development and disease response programs in plants. Regulation of these distinct survival programs by a single transcription factor may ensure optimal allocation of plant resources for reproductive fitness. Expression array analysis used to identify genes differentially expressed upon LFY induction in 9-day-old shoot apices.
Project description:The transition from vegetative growth to flower formation is critical for the survival of flowering plants. The plant-specific transcription factor LEAFY (LFY) has central, evolutionarily conserved roles in this process, both in the formation of the first flower and later in floral patterning. We performed genome-wide binding and expression studies to elucidate the molecular mechanisms by which LFY executes these roles. Our study reveals that LFY directs an intricate regulatory network in control of floral homeotic gene expression and, unexpectedly, controls the expression of genes regulating the response to external stimuli in Arabidopsis. We further show that LFY dampens responses to a bacterial MAMP (microbe-associated molecular pattern) and to pathogen challenge. Our findings suggest a molecular mechanism for the coordination of reproductive stage development and disease response programs in plants. Regulation of these distinct survival programs by a single transcription factor may ensure optimal allocation of plant resources for reproductive fitness. Genome binding/occupancy profiling by genome tiling array used to identity genes bound by endogenous LFY in inflorescences.
Project description:The transition from vegetative growth to flower formation is critical for the survival of flowering plants. The plant-specific transcription factor LEAFY (LFY) has central, evolutionarily conserved roles in this process, both in the formation of the first flower and later in floral patterning. We performed genome-wide binding and expression studies to elucidate the molecular mechanisms by which LFY executes these roles. Our study reveals that LFY directs an intricate regulatory network in control of floral homeotic gene expression and, unexpectedly, controls the expression of genes regulating the response to external stimuli in Arabidopsis. We further show that LFY dampens responses to a bacterial MAMP (microbe-associated molecular pattern) and to pathogen challenge. Our findings suggest a molecular mechanism for the coordination of reproductive stage development and disease response programs in plants. Regulation of these distinct survival programs by a single transcription factor may ensure optimal allocation of plant resources for reproductive fitness. Genome binding/occupancy profiling by genome tiling array used to identity genes bound by induced LFY in 9-day-old seedlings.
Project description:The transition from vegetative growth to flower formation is critical for the survival of flowering plants. The plant-specific transcription factor LEAFY (LFY) has central, evolutionarily conserved roles in this process, both in the formation of the first flower and later in floral patterning. We performed genome-wide binding and expression studies to elucidate the molecular mechanisms by which LFY executes these roles. Our study reveals that LFY directs an intricate regulatory network in control of floral homeotic gene expression and, unexpectedly, controls the expression of genes regulating the response to external stimuli in Arabidopsis. We further show that LFY dampens responses to a bacterial MAMP (microbe-associated molecular pattern) and to pathogen challenge. Our findings suggest a molecular mechanism for the coordination of reproductive stage development and disease response programs in plants. Regulation of these distinct survival programs by a single transcription factor may ensure optimal allocation of plant resources for reproductive fitness. Expression array analysis used to identify genes differentially expressed upon LFY induction in 9-day-old shoot apices. Expression array analysis of 9-day-old 35S::LFY-GR dexamethasone-treated seedlings compared to 9-day-old WT dexamethasone-treated seedlings. Four biological replicate samples.
Project description:The peanut witches' broom (PnWB) phytoplasma causes virescence symptoms such as phyllody (leafy flower) in infected peanuts. However, the obligate nature of phytoplasma limits the study of host-pathogen interactions, and the detailed anatomy of PnWB-infected plants has yet to be reported. Here, we demonstrate that 4',6'-diamidino-2-phenylindole (DAPI) staining can be used to track PnWB infection. The DAPI-stained phytoplasma cells were observed in phloem/internal phloem tissues, and changes in vascular bundle morphology, including increasing pith rays and thinner cell walls in the xylem, were found. We also discerned the cell types comprising PnWB in infected sieve tube members. These results suggest that the presence of PnWB in phloem tissue facilitates the transmission of phytoplasma via sap-feeding insect vectors. In addition, PnWB in sieve tube members and changes in vascular bundle morphology might strongly promote the ability of phytoplasmas to assimilate nutrients. These data will help further an understanding of the obligate life cycle and host-pathogen interactions of phytoplasma.
Project description:The switch from vegetative to reproductive development in plants necessitates a switch in the developmental program of the descendents of the stem cells in the shoot apical meristem. Genetic and molecular investigations have demonstrated that the plant-specific transcription factor and meristem identity regulator LEAFY (LFY) controls this developmental transition by inducing expression of a second transcription factor, APETALA1, and by regulating the expression of additional, as yet unknown, genes. Here we show that the additional LFY targets include the APETALA1-related factor, CAULIFLOWER, as well as three transcription factors and two putative signal transduction pathway components. These genes are up-regulated by LFY even when protein synthesis is inhibited and, hence, appear to be direct targets of LFY. Supporting this conclusion, cis-regulatory regions upstream of these genes are bound by LFY in vivo. The newly identified LFY targets likely initiate the transcriptional changes that are required for the switch from vegetative to reproductive development in Arabidopsis.
Project description:Floral organs, whose identity is determined by specific combinations of homeotic genes, originate from a group of undifferentiated cells called the floral meristem. In Arabidopsis, the homeotic gene AGAMOUS (AG) terminates meristem activity and promotes development of stamens and carpels. To understand the program of gene expression activated by AG, we followed genome-wide expression during early stamen and carpel development. Keywords: Developmental time course
Project description:Although genome-wide studies have identified a number of candidate regions evolving under selection in domesticated animals and cultivated plants, few attempts have been made, from the point of a definite biological process, to assess sequence variation and characterize the regimes of the selection on miRNA-associated motifs. Here, we performed a genome-wide dissection of nucleotide variation and selection of miRNA targets associated with rice flower development. By sampling and resequencing 26 miRNA targets for globally diverse representative populations of Asian cultivated rice and wild relatives, we found that purifying selection has reduced genetic variation at the conserved miRNA binding sites on the whole, and highly conserved miRNA binding sequences were maintained in the studied rice populations. Conversely, non-neutral evolution of positive and/or artificial selection accelerates the elevated variations at nonconserved binding sites in a population-specific behavior which may have contributed to flower development-related phenotypic variation. Taken together, our results elucidate that miRNA targets involved in flower development are under distinctive selection regimes during rice evolution.
Project description:The floral meristem (FM) is self-maintaining at the early stages of flower development, but it is terminated when a fixed number of floral organs are produced. The FLORAL ORGAN NUMBER4 (FON4; also known as FON2) gene, an ortholog of Arabidopsis CLAVATA3 (CLV3), is required for regulating FM size and determinacy in rice. However, its interactions with floral homeotic genes remain unknown. Here, we report the genetic interactions between FON4 and floral homeotic genes OsMADS15 (an A-class gene), OsMADS16 (also called SUPERWOMAN1, SPW1, a B-class gene), OsMADS3 and OsMADS58 (C-class genes), OsMADS13 (a D-class gene), and OsMADS1 (an E-class gene) during flower development. We observed an additive phenotype in the fon4 double mutant with the OsMADS15 mutant allele dep (degenerative palea). The effect on the organ number of whorl 2 was enhanced in fon4 spw1. Double mutant combinations of fon4 with osmads3, osmads58, osmads13, and osmads1 displayed enhanced defects in FM determinacy and identity, respectively, indicating that FON4 and these genes synergistically control FM activity. In addition, the expression patterns of all the genes besides OsMADS13 had no obvious change in the fon4 mutant. This work reveals how the meristem maintenance gene FON4 genetically interacts with C, D, and E floral homeotic genes in specifying FM activity in monocot rice.
Project description:Flowers are the most complex structures of plants. Studies of Arabidopsis thaliana, which has typical eudicot flowers, have been fundamental in advancing the structural and molecular understanding of flower development. The main processes and stages of Arabidopsis flower development are summarized to provide a framework in which to interpret the detailed molecular genetic studies of genes assigned functions during flower development and is extended to recent genomics studies uncovering the key regulatory modules involved. Computational models have been used to study the concerted action and dynamics of the gene regulatory module that underlies patterning of the Arabidopsis inflorescence meristem and specification of the primordial cell types during early stages of flower development. This includes the gene combinations that specify sepal, petal, stamen and carpel identity, and genes that interact with them. As a dynamic gene regulatory network this module has been shown to converge to stable multigenic profiles that depend upon the overall network topology and are thus robust, which can explain the canalization of flower organ determination and the overall conservation of the basic flower plan among eudicots. Comparative and evolutionary approaches derived from Arabidopsis studies pave the way to studying the molecular basis of diverse floral morphologies.