A genetic and molecular model for flower development in Arabidopsis thaliana

Cells in developing organisms do not only differentiate, they differentiate in defined patterns. A striking example is the differentiation of flowers, which in most plant families consist of four types of organs: sepals, petals, stamens and carpels, each composed of characteristic cell types. In the families of flowering plants in which these organs occur, they are patterned with the sepals in the outermost whorl or whorls of the flower, with the petals next closest to the center, the stamens even closer to the center, and the carpels central. In each species of flowering plant the disposition and number (or range of numbers) of these organs is also specified, and the floral ‘formula’ is repeated in each of the flowers on each individual plant of the species. We do not know how cells in developing plants determine their position, and in response to this determination differentiate to the cell types appropriate for that position. While there have been a number of speculative proposals for the mechanism of organ specification in flowers (Goethe, 1790; Goebel, 1900; Heslop-Harrison, 1964; Green, 1988), recent genetic evidence is inconsistent with all of them, at least in the forms in which they were originally presented (Bowman et al. 1989; Meyerowitz et al. 1989). We describe here a preliminary model, based on experiments with Arabidopsis thaliana. The model is by and large consistent with existing evidence, and has predicted the results of a number of genetic and molecular experiments that have been recently performed.

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Opposing macroevolutionary and trait-mediated patterns of threat and naturalization in flowering plants

10.1101/2020.07.24.219667 ◽

2020 ◽

Author(s):

J. P. Schmidt ◽

T. J. Davies ◽

M. J. Farrell

Keyword(s):

Climate Variability ◽

Generation Time ◽

Native Species ◽

Flowering Plants ◽

The Other ◽

Flowering Plant ◽

Evolutionary Time ◽

Short Generation Time ◽

Plant Families ◽

Time Autonomous

AbstractDue to expanding global trade and movement, new plant species are establishing in exotic ranges at increasing rates while the number of native species facing extinction from multiple threats grows. Yet, how species losses and gains globally may together be linked to traits and macroevolutionary processes is poorly understood. Here we show that, adjusting for diversification rate and age, the proportion of threatened species across flowering plant families is negatively related to the proportion of naturalized species. Moreover, naturalization is positively associated with climate variability, short generation time, autonomous seed production, and interspecific hybridization, but negatively with age and diversification; whereas threat is negatively associated with climate variability and hybridization, and positively with biotic pollination, age and diversification. Such a pronounced signature of naturalization and threat across plant families suggests that both trait syndromes have coexisted over deep evolutionary time and that neither strategy is necessarily superior to the other.

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Functional innovations of PIN auxin transporters mark crucial evolutionary transitions during rise of flowering plants

Science Advances ◽

10.1126/sciadv.abc8895 ◽

2020 ◽

Vol 6 (50) ◽

pp. eabc8895

Author(s):

Yuzhou Zhang ◽

Lesia Rodriguez ◽

Lanxin Li ◽

Xixi Zhang ◽

Jiří Friml

Keyword(s):

Critical Role ◽

Cell Types ◽

Floral Organ ◽

Flowering Plants ◽

Flowering Plant ◽

Evolutionary Transitions ◽

Coding Regions ◽

Essential Components ◽

Complex Architecture

Flowering plants display the highest diversity among plant species and have notably shaped terrestrial landscapes. Nonetheless, the evolutionary origin of their unprecedented morphological complexity remains largely an enigma. Here, we show that the coevolution of cis-regulatory and coding regions of PIN-FORMED (PIN) auxin transporters confined their expression to certain cell types and directed their subcellular localization to particular cell sides, which together enabled dynamic auxin gradients across tissues critical to the complex architecture of flowering plants. Extensive intraspecies and interspecies genetic complementation experiments with PINs from green alga up to flowering plant lineages showed that PIN genes underwent three subsequent, critical evolutionary innovations and thus acquired a triple function to regulate the development of three essential components of the flowering plant Arabidopsis: shoot/root, inflorescence, and floral organ. Our work highlights the critical role of functional innovations within the PIN gene family as essential prerequisites for the origin of flowering plants.

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Brassinosteroids repress the seed maturation program during the seed-to-seedling transition

Plant Physiology ◽

10.1093/plphys/kiab089 ◽

2021 ◽

Author(s):

Jiuxiao Ruan ◽

Huhui Chen ◽

Tao Zhu ◽

Yaoguang Yu ◽

Yawen Lei ◽

...

Keyword(s):

Arabidopsis Thaliana ◽

Transcription Factor ◽

Abscisic Acid ◽

Plant Hormone ◽

Flowering Plants ◽

Seed Maturation ◽

Domain Protein ◽

Abscisic Acid Insensitive3 ◽

Underlying Mechanisms ◽

Embryonic Structure

Abstract In flowering plants, repression of the seed maturation program is essential for the transition from the seed to the vegetative phase, but the underlying mechanisms remain poorly understood. The B3-domain protein VIVIPAROUS1/ABSCISIC ACID-INSENSITIVE3-LIKE 1 (VAL1) is involved in repressing the seed maturation program. Here we uncovered a molecular network triggered by the plant hormone brassinosteroid (BR) that inhibits the seed maturation program during the seed-to-seedling transition in Arabidopsis (Arabidopsis thaliana). val1-2 mutant seedlings treated with a BR biosynthesis inhibitor form embryonic structures, whereas BR signaling gain-of-function mutations rescue the embryonic structure trait. Furthermore, the BR-activated transcription factors BRI1-EMS-SUPPRESSOR 1 and BRASSINAZOLE-RESISTANT 1 bind directly to the promoter of AGAMOUS-LIKE15 (AGL15), which encodes a transcription factor involved in activating the seed maturation program, and suppress its expression. Genetic analysis indicated that BR signaling is epistatic to AGL15 and represses the seed maturation program by downregulating AGL15. Finally, we showed that the BR-mediated pathway functions synergistically with the VAL1/2-mediated pathway to ensure the full repression of the seed maturation program. Together, our work uncovered a mechanism underlying the suppression of the seed maturation program, shedding light on how BR promotes seedling growth.

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Stomatal Development in the Context of Epidermal Tissues

Annals of Botany ◽

10.1093/aob/mcab052 ◽

2021 ◽

Author(s):

Keiko U Torii

Keyword(s):

Arabidopsis Thaliana ◽

Molecular Genetic ◽

Cell Lineage ◽

Optimal Growth ◽

Cell Types ◽

State Transitions ◽

Stomatal Development ◽

Water Control ◽

Pavement Cells ◽

The Core

Abstract Background Stomata are adjustable pores on the surface of plant shoots for efficient gas exchange and water control. The presence of stomata is essential for plant growth and survival, and the evolution of stomata is considered as a key developmental innovation of the land plants, allowing colonization on land from aquatic environments some 450 million years ago. In the past two decades, molecular genetic studies using the model plant Arabidopsis thaliana identified key genes and signalling modules that regulate stomatal development: master-regulatory transcription factors that orchestrate cell-state transitions and peptide-receptor signal transduction pathways, which, together, enforce proper patterning of stomata within the epidermis. Studies in diverse plant species, ranging from bryophytes to angiosperm grasses, have begun to unravel the conservation and uniqueness of the core modules in stomatal development. Scope Here, I review the mechanisms of stomatal development in the context of epidermal tissue patterning. First, I introduce the core regulatory mechanisms of stomatal patterning and differentiation in the model species Arabidopsis thaliana. Subsequently, experimental evidence is presented supporting the idea that different cell types within the leaf epidermis, namely stomata, hydathodes pores, pavement cells, and trichomes, either share developmental origins or mutually influence each other’s gene regulatory circuits during development. Emphasis is taken on extrinsic and intrinsic signals regulating the balance between stomata and pavement cells, specifically by controlling the fate of Stomatal-Lineage Ground Cells (SLGCs) to remain within the stomatal-cell lineage or differentiate into pavement cells. Finally, I discuss the influence of inter-tissue-layer communication between the epidermis and underlying mesophyll/vascular tissues on stomatal differentiation. Understanding the dynamic behaviors of stomatal precursor cells and their differentiation in the broader context of tissue and organ development may help design plants tailored for optimal growth and productivity in specific agricultural applications and a changing environment.

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Orchid Bsister gene PeMADS28 displays conserved function in ovule integument development

Scientific Reports ◽

10.1038/s41598-020-79877-9 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Ching-Yu Shen ◽

You-Yi Chen ◽

Ke-Wei Liu ◽

Hsiang-Chia Lu ◽

Song-Bin Chang ◽

...

Keyword(s):

Arabidopsis Thaliana ◽

Protein Interaction ◽

Ectopic Expression ◽

Flowering Plants ◽

Complementation Test ◽

Ovule Development ◽

Mads Box ◽

Temporal Expression ◽

Protein Protein Interaction ◽

Silique Length

AbstractThe ovules and egg cells are well developed to be fertilized at anthesis in many flowering plants. However, ovule development is triggered by pollination in most orchids. In this study, we characterized the function of a Bsister gene, named PeMADS28, isolated from Phalaenopsis equestris, the genome-sequenced orchid. Spatial and temporal expression analysis showed PeMADS28 predominantly expressed in ovules between 32 and 48 days after pollination, which synchronizes with integument development. Subcellular localization and protein–protein interaction analyses revealed that PeMADS28 could form a homodimer as well as heterodimers with D-class and E-class MADS-box proteins. In addition, ectopic expression of PeMADS28 in Arabidopsis thaliana induced small curled rosette leaves, short silique length and few seeds, similar to that with overexpression of other species’ Bsister genes in Arabidopsis. Furthermore, complementation test revealed that PeMADS28 could rescue the phenotype of the ABS/TT16 mutant. Together, these results indicate the conserved function of BsisterPeMADS28 associated with ovule integument development in orchid.

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Flowering plant embryos: How did we end up here?

Plant Reproduction ◽

10.1007/s00497-021-00427-y ◽

2021 ◽

Author(s):

Stefan A. Rensing ◽

Dolf Weijers

Keyword(s):

Current Knowledge ◽

General Structure ◽

Three Dimensional ◽

Flowering Plants ◽

Flowering Plant ◽

Adult Plant ◽

Ancestral State ◽

Evolutionary Trajectory ◽

Current State ◽

Plant Embryo

AbstractThe seeds of flowering plants are sexually produced propagules that ensure dispersal and resilience of the next generation. Seeds harbor embryos, three dimensional structures that are often miniatures of the adult plant in terms of general structure and primordial organs. In addition, embryos contain the meristems that give rise to post-embryonically generated structures. However common, flowering plant embryos are an evolutionary derived state. Flowering plants are part of a much larger group of embryo-bearing plants, aptly termed Embryophyta. A key question is what evolutionary trajectory led to the emergence of flowering plant embryos. In this opinion, we deconstruct the flowering plant embryo and describe the current state of knowledge of embryos in other plant lineages. While we are far yet from understanding the ancestral state of plant embryogenesis, we argue what current knowledge may suggest and how the knowledge gaps may be closed.

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John O. Kokwaro, Flowering Plant Families of East Africa: an introduction to plant taxonomy. Nairobi: East African Educational Publishers, 1994, 292 pp., £14.95, ISBN 9966 46 4905 (distributed in the UK by African Books Collective, 27 Park End Street, Oxford OX1 1HU).

Africa ◽

10.2307/1161335 ◽

1996 ◽

Vol 66 (2) ◽

pp. 321-321

Author(s):

Bernard W. Riley ◽

David Brokensha

Keyword(s):

East Africa ◽

Flowering Plant ◽

Plant Taxonomy ◽

East African ◽

Plant Families ◽

The Uk

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An Analysis of Microsatellite Loci in Arabidopsis thaliana: Mutational Dynamics and Application

Genetics ◽

10.1093/genetics/165.3.1475 ◽

2003 ◽

Vol 165 (3) ◽

pp. 1475-1488

Author(s):

V Vaughan Symonds ◽

Alan M Lloyd

Keyword(s):

Arabidopsis Thaliana ◽

Microsatellite Loci ◽

Current Knowledge ◽

Flowering Plant ◽

Allele Frequency Distribution ◽

Strongly Correlated ◽

Microsatellite Evolution ◽

Stepwise Mutation ◽

Mutation Pattern ◽

Infinite Alleles Model

Abstract Microsatellite loci are among the most commonly used molecular markers. These loci typically exhibit variation for allele frequency distribution within a species. However, the factors contributing to this variation are not well understood. To expand on the current knowledge of microsatellite evolution, 20 microsatellite loci were examined for 126 accessions of the flowering plant, Arabidopsis thaliana. Substantial variability in mutation pattern among loci was found, most of which cannot be explained by the assumptions of the traditional stepwise mutation model or infinite alleles model. Here it is shown that the degree of locus diversity is strongly correlated with the number of contiguous repeats, more so than with the total number of repeats. These findings support a strong role for repeat disruptions in stabilizing microsatellite loci by reducing the substrate for polymerase slippage and recombination. Results of cluster analyses are also presented, demonstrating the potential of microsatellite loci for resolving relationships among accessions of A. thaliana.

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