skip to main content


Title: Lateral Leaflet Suppression 1 ( LLS1 ), encoding the MtYUCCA1 protein, regulates lateral leaflet development in Medicago truncatula
Summary

In species with compound leaves, the positions of leaflet primordium initiation are associated with local peaks of auxin accumulation. However, the role of auxin during the late developmental stages and outgrowth of compound leaves remains largely unknown.

Using genome resequencing approaches, we identified insertion sites at four alleles of theLATERAL LEAFLET SUPPRESSION1(LLS1) gene, encoding the auxin biosynthetic enzyme YUCCA1 inMedicago truncatula.

Linkage analysis and complementation tests showed that thells1mutant phenotypes were caused by theTnt1insertions that disrupted theLLS1gene. The transcripts ofLLS1can be detected in primordia at early stages of leaf initiation and later in the basal regions of leaflets, and finally in vein tissues at late leaf developmental stages. Vein numbers and auxin content are reduced in thells1‐1mutant. Analysis of thells1 sgl1andlls1 palm1double mutants revealed thatSGL1is epistatic toLLS1, andLLS1works withPALM1in an independent pathway to regulate the growth of lateral leaflets.

Our work demonstrates that the YUCCA1/YUCCA4 subgroup plays very important roles in the outgrowth of lateral leaflets during compound leaf development ofM. truncatula, in addition to leaf venation.

 
more » « less
NSF-PAR ID:
10401917
Author(s) / Creator(s):
 ;  ;  ;  ;  ;  ;  ;  ;  ;  ;  ;  ;  ;  
Publisher / Repository:
Wiley-Blackwell
Date Published:
Journal Name:
New Phytologist
Volume:
227
Issue:
2
ISSN:
0028-646X
Page Range / eLocation ID:
p. 613-628
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. Summary

    Style length is a major determinant of breeding strategies in flowering plants and can vary dramatically between and within species. However, little is known about the genetic and developmental control of style elongation.

    We characterized the role of two classes of leaf adaxial–abaxial polarity factors, SUPPRESSOR OF GENE SILENCING3 (SGS3) and the YABBY family transcription factors, in the regulation of style elongation inMimulus lewisii. We also examined the spatiotemporal patterns of auxin response during style development.

    Loss ofSGS3function led to reduced style length via limiting cell division, and downregulation ofYABBYgenes by RNA interference resulted in shorter styles by decreasing both cell division and cell elongation. We discovered an auxin response minimum between the stigma and ovary during the early stages of pistil development that marks style differentiation. Subsequent redistribution of auxin response to this region was correlated with style elongation. Auxin response was substantially altered when bothSGS3andYABBYfunctions were disrupted.

    We suggest that auxin signaling plays a central role in style elongation and that the way in which auxin signaling controls the different cell division and elongation patterns underpinning natural style length variation is a major question for future research.

     
    more » « less
  2. SUMMARY

    Flowering of the reference legumeMedicago truncatulais promoted by winter cold (vernalization) followed by long‐day photoperiods (VLD) similar to winter annual Arabidopsis. However, Medicago lacksFLCandCO, key regulators of Arabidopsis VLD flowering.Most plants have twoINHIBITOR OF GROWTH(ING) genes (ING1andING2), encoding proteins with an ING domain with two anti‐parallel alpha‐helices and a plant homeodomain (PHD) finger, but their genetic role has not been previously described.In Medicago,Mting1gene‐edited mutants developed and flowered normally, but anMting2‐1 Tnt1insertion mutant and gene‐editedMting2mutants had developmental abnormalities including delayed flowering particularly in VLD, compact architecture, abnormal leaves with extra leaflets but no trichomes, and smaller seeds and barrels.Mting2mutants had reduced expression of activators of flowering, including theFT‐like geneMtFTa1, and increased expression of the candidate repressorMtTFL1c, consistent with the delayed flowering of the mutant.MtING2overexpression complementedMting2‐1, but did not accelerate flowering in wild type. The MtING2 PHD finger bound H3K4me2/3 peptides weaklyin vitro, but analysis of gene‐edited mutants indicated that it was dispensable to MtING2 function in wild‐type plants. RNA sequencing experiments indicated that >7000 genes are mis‐expressed in theMting2‐1mutant, consistent with its strong mutant phenotypes. Interestingly, ChIP‐seq analysis identified >5000 novel H3K4me3 locations in the genome ofMting2‐1mutants compared to wild type R108. Overall, our mutant study has uncovered an important physiological role of a plantING2gene in development, flowering, and gene expression, which likely involves an epigenetic mechanism.

     
    more » « less
  3. Abstract

    Mungbean (Vigna radiata(L.) Wizcek) is an important pulse crop, increasingly used as a source of protein, fiber, low fat, carbohydrates, minerals, and bioactive compounds in human diets. Mungbean is a dicot plant with trifoliate leaves. The primary component of many plant functions, including photosynthesis, light interception, and canopy structure, are leaves. The objectives were to investigate leaf morphological attributes, use image analysis to extract leaf morphological traits from photos from the Iowa Mungbean Diversity (IMD) panel, create a regression model to predict leaflet area, and undertake association mapping. We collected over 5000 leaf images of the IMD panel consisting of 484 accessions over 2 years (2020 and 2021) with two replications per experiment. Leaf traits were extracted using image analysis, analyzed, and used for association mapping. Morphological diversity included leaflet type (oval or lobed), leaflet size (small, medium, large), lobed angle (shallow, deep), and vein coloration (green, purple). A regression model was developed to predict each ovate leaflet's area (adjustedR2 = 0.97; residual standard errors of < = 1.10). The candidate genesVradi01g07560,Vradi05g01240,Vradi02g05730, andVradi03g00440are associated with multiple traits (length, width, perimeter, and area) across the leaflets (left, terminal, and right). These are suitable candidate genes for further investigation in their role in leaf development, growth, and function. Future studies will be needed to correlate the observed traits discussed here with yield or important agronomic traits for use as phenotypic or genotypic markers in marker‐aided selection methods for mungbean crop improvement.

     
    more » « less
  4. Summary

    Abscission is predetermined in specialized cell layers called the abscission zone (AZ) and activated by developmental or environmental signals. In the grass family, most identified AZ genes regulate AZ anatomy, which differs among lineages. A YABBY transcription factor,SHATTERING1(SH1), is a domestication gene regulating abscission in multiple cereals, including rice andSetaria. In rice,SH1inhibits lignification specifically in the AZ. However, the AZ ofSetariais nonlignified throughout, raising the question of howSH1functions in species without lignification.

    Crispr‐Cas9 knockout mutants ofSH1were generated inSetaria viridisand characterized with histology, cell wall and auxin immunofluorescence, transmission electron microscopy, hormonal treatment and RNA‐Seq analysis.

    Thesh1mutant lacks shattering, as expected. No differences in cell anatomy or cell wall components including lignin were observed betweensh1and the wild‐type (WT) until abscission occurs. Chloroplasts degenerated in the AZ of WT before abscission, but degeneration was suppressed by auxin treatment. Auxin distribution and expression of auxin‐related genes differed between WT andsh1, with the signal of an antibody to auxin detected in thesh1chloroplast.

    SH1inSetariais required for activation of abscission through auxin signaling, which is not reported in other grass species.

     
    more » « less
  5. Abstract

    Crosstalk between auxin and cytokinin contributes to widespread developmental processes, including root and shoot meristem maintenance, phyllotaxy, and vascular patterning. However, our understanding of crosstalk between these hormones is limited primarily to angiosperms. The moss Physcomitrium patens (formerly Physcomitrella patens) is a powerful system for studying plant hormone function. Auxin and cytokinin play similar roles in regulating moss gametophore (shoot) architecture, to those in flowering plant shoots. However, auxin–cytokinin crosstalk is poorly understood in moss. Here we find that the ratio of auxin to cytokinin is an important determinant of development in P. patens, especially during leaf development and branch stem cell initiation. Addition of high levels of auxin to P. patens gametophores blocks leaf outgrowth. However, simultaneous addition of high levels of both auxin and cytokinin partially restores leaf outgrowth, suggesting that the ratio of these hormones is the predominant factor. Likewise, during branch initiation and outgrowth, chemical inhibition of auxin synthesis phenocopies cytokinin application. Finally, cytokinin-insensitive mutants resemble plants with altered auxin signaling and are hypersensitive to auxin. In summary, our results suggest that the ratio between auxin and cytokinin signaling is the basis for developmental decisions in the moss gametophore.

     
    more » « less