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Title: RNA interference suppression of AGAMOUS and SEEDSTICK alters floral organ identity and impairs floral organ determinacy, ovule differentiation, and seed‐hair development in Populus
Author(s) / Creator(s):
 ;  ;  ;  ;  ;  ;  ;  
Publisher / Repository:
Date Published:
Journal Name:
New Phytologist
Page Range / eLocation ID:
p. 923-937
Medium: X
Sponsoring Org:
National Science Foundation
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  1. Summary

    Plant lateral organ development is a complex process involving both transcriptional activation and repression mechanisms. TheWOXtranscriptional repressorWOX1/STF, theLEUNIG(LUG) transcriptional corepressor and theANGUSTIFOLIA3 (AN3) transcriptional coactivator play important roles in leaf blade outgrowth and flower development, but how these factors coordinate their activities remains unclear. Here we report physical and genetic interactions among these key regulators of leaf and flower development.

    We developed a novelin plantatranscriptional activation/repression assay and suggest thatLUGcould function as a transcriptional coactivator during leaf blade development.

    MtLUGphysically interacts with MtAN3, and this interaction appears to be required for leaf and flower development. A single amino acid substitution at position 61 in theSNHdomain of MtAN3 protein abolishes its interaction with MtLUG, and its transactivation activity and biological function. Mutations inlugandan3enhanced each other's mutant phenotypes. Both thelugand thean3mutations enhanced thewox1 prsleaf and flower phenotypes inArabidopsis.

    Our findings together suggest that transcriptional repression and activation mediated by theWOX,LUGandAN3 regulators function in concert to promote leaf and flower development, providing novel mechanistic insights into the complex regulation of plant lateral organ development.

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  2. Floral development is one of the model systems for investigating the mechanisms underlying organogenesis in plants. Floral organ identity is controlled by the well-known ABC model, which has been generalized to many flowering plants. Here, we report a previously uncharacterized MYB-like gene,AGAMOUS-LIKE FLOWER(AGLF), involved in flower development in the model legumeMedicago truncatula. Loss-of-function ofAGLFresults in flowers with stamens and carpel transformed into extra whorls of petals and sepals. Compared with the loss-of-function mutant of the class C geneAGAMOUS(MtAG) inM. truncatula, the defects in floral organ identity are similar betweenaglfandmtag, but the floral indeterminacy is enhanced in theaglfmutant. Knockout ofAGLFin the mutants of the class A geneMtAP1or the class B geneMtPIleads to an addition of a loss-of-C-function phenotype, reflecting a conventional relationship ofAGLFwith the canonical A and B genes. Furthermore, we demonstrate thatAGLFactivatesMtAGin transcriptional levels in control of floral organ identity. These data shed light on the conserved and diverged molecular mechanisms that control flower development and morphology among plant species.

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    Hypophthalmichthys molitrix,silver carp, is an invasive Asian carp that has become increasingly widespread and ecologically destructive within the upper Mississippi River Basin. Its complex trophic anatomy may help explain the apparent efficiency with which they consume phytoplankton, outcompeting native filter feeders. This cypriniform species is characterized by trophic synapomorphies that include a palatal organ, loss of upper pharyngeal jaws, and a hypertrophied lower pharyngeal jaw. However, in silver carp these structures have become greatly modified and diverge from the more basal condition that characterizes species such as goldfish. The trophic apparatus of silver carp is composed of discrete structures that are functionally coupled: filtering plates, paired epibranchial organs (EBO), a modified palatal organ composed of large muscular folds that interdigitate with the filtering plates, and hypertrophied lower pharyngeal jaws and teeth. The filtering plates fill a significant portion of the buccal cavity, especially since the distal parts of these filtering plates make up a key component of the EBOs. EBOs, food aggregating structures found in many teleosts, are thought to have independently evolved at least six times. Ranging in complexity from small slits on the dorsal wall of the pharyngeal cavity to exceedingly intricate spiraling structures, EBOs are morphologically diverse among filter‐feeding fishes. Despite this morphological diversity and broad taxonomic distribution, little is known regarding the functional anatomy of the EBO. Moreover, the EBO in silver carp is distinct from the organs previously described in other species, being created by four independent pharyngeal involutions (instead of the more typical one or two) that form spiral‐shaped pharyngeal tubes surrounded by circumferential muscle. On each side of the head greatly hypertrophied hyomandibulae and opercles are connected to the anterior cartilaginous caps of the bilateral EBOs via enlarged muscles. Given that these fish are pump filter feeders we hypothesize that the opercula may compress and expand the EBOs during pumping causing food to be moved posteriorly toward the pharyngeal jaws.

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  5. null (Ed.)
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