SHATTERPROOF 2 regulates TAA1 expression for the establishment of the gynoecium valve margins. Gynoecium development and patterning play a crucial role in determining the ultimate structure of the fruit and, thus, seed production. The MADS-box transcription factor SHATTERPROOF 2 (SHP2) contributes to valve margin differentiation and plays a major role in fruit dehiscence and seed dispersal. Despite the acknowledged contribution of auxin to gynoecium development, its precise role in valve margin establishment remains somewhat enigmatic. Our study addresses this gap by uncovering the role of SHP2 as a positive regulator of key auxin biosynthetic genes, TAA1 and YUCCA 4. Genetic and molecular analyses revealed that SHP2 directly regulates the expression of TAA1 in the valve margins of a stage 12 gynoecium with known regulators of flower and ovule development, such as AGAMOUS, SEEDSTICK, and SEPATALA 3. Collectively, our findings define a previously unrecognized function of SHP2 in the regulation of auxin biosynthetic genes during gynoecium development and raise the possibility that the auxin produced under SHP2 regulation may contribute significantly to the valve margin establishment.

• Keywords
• Auxin, Gynoecium, SHATTERPROOF 2, TAA1, Valve margins, YUCCA 4,
• MeSH
• Arabidopsis * genetics   metabolism   growth & development   MeSH
• Flowers genetics   metabolism   growth & development   MeSH
• Indoleacetic Acids metabolism   MeSH
• MADS Domain Proteins * genetics   metabolism   MeSH
• Arabidopsis Proteins * metabolism   genetics   MeSH
• Gene Expression Regulation, Plant * MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Indoleacetic Acids MeSH
• MADS Domain Proteins * MeSH
• Arabidopsis Proteins * MeSH
• SHP2 protein, Arabidopsis MeSH Browser

BACKGROUND: The increasing ambient temperature significantly impacts plant growth, development, and reproduction. Uncovering the temperature-regulating mechanisms in plants is of high importance, for increasing our fundamental understanding of plant thermomorphogenesis, for its potential in applied science, and for aiding plant breeders in improving plant thermoresilience. Thermomorphogenesis, the developmental response to warm temperatures, has been primarily studied in seedlings and in the regulation of flowering time. PHYTOCHROME B and PHYTOCHROME-INTERACTING FACTORs (PIFs), particularly PIF4, are key components of this response. However, the thermoresponse of other adult vegetative tissues and reproductive structures has not been systematically evaluated, especially concerning the involvement of phyB and PIFs. RESULTS: We screened the temperature responses of the wild type and several phyB-PIF4 pathway Arabidopsis mutant lines in combined and integrative phenotyping platforms for root growth in soil, shoot, inflorescence, and seed. Our findings demonstrate that phyB-PIF4 is generally involved in the relay of temperature signals throughout plant development, including the reproductive stage. Furthermore, we identified correlative responses to high ambient temperature between shoot and root tissues. This integrative and automated phenotyping was complemented by monitoring the changes in transcript levels in reproductive organs. Transcriptomic profiling of the pistils from plants grown under high ambient temperature identified key elements that may provide insight into the molecular mechanisms behind temperature-induced reduced fertilization rate. These include a downregulation of auxin metabolism, upregulation of genes involved auxin signalling, miRNA156 and miRNA160 pathways, and pollen tube attractants. CONCLUSIONS: Our findings demonstrate that phyB-PIF4 involvement in the interpretation of temperature signals is pervasive throughout plant development, including processes directly linked to reproduction.

• Keywords
• Arabidopsis, Automatic phenotyping, PIF4, Pistils, Pollen tube guidance, Seeds, Thermomorphogenesis, phyB,
• MeSH
• Arabidopsis * genetics   metabolism   growth & development   physiology   MeSH
• Phenotype * MeSH
• Phytochrome B * metabolism   genetics   MeSH
• Plant Roots genetics   metabolism   growth & development   MeSH
• Flowers genetics   growth & development   MeSH
• Arabidopsis Proteins * genetics   metabolism   MeSH
• Gene Expression Regulation, Plant MeSH
• Signal Transduction MeSH
• Basic Helix-Loop-Helix Transcription Factors * genetics   metabolism   MeSH
• Hot Temperature MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Phytochrome B * MeSH
• PHYB protein, Arabidopsis MeSH Browser
• PIF4 protein, Arabidopsis MeSH Browser
• Arabidopsis Proteins * MeSH
• Basic Helix-Loop-Helix Transcription Factors * MeSH

Much of plant development depends on cell-to-cell redistribution of the plant hormone auxin, which is facilitated by the plasma membrane (PM) localized PIN FORMED (PIN) proteins. Auxin export activity, developmental roles, subcellular trafficking, and polarity of PINs have been well studied, but their structure remains elusive besides a rough outline that they contain two groups of 5 alpha-helices connected by a large hydrophilic loop (HL). Here, we focus on the PIN1 HL as we could produce it in sufficient quantities for biochemical investigations to provide insights into its secondary structure. Circular dichroism (CD) studies revealed its nature as an intrinsically disordered protein (IDP), manifested by the increase of structure content upon thermal melting. Consistent with IDPs serving as interaction platforms, PIN1 loops homodimerize. PIN1 HL cytoplasmic overexpression in Arabidopsis disrupts early endocytic trafficking of PIN1 and PIN2 and causes defects in the cotyledon vasculature formation. In summary, we demonstrate that PIN1 HL has an intrinsically disordered nature, which must be considered to gain further structural insights. Some secondary structures may form transiently during pairing with known and yet-to-be-discovered interactors.

• Keywords
• PIN1, dimerization, hydrophilic hoop, intrinsic disorder, subcellular trafficking,
• MeSH
• Arabidopsis * metabolism   MeSH
• Biological Transport MeSH
• Plant Roots metabolism   MeSH
• Indoleacetic Acids metabolism   MeSH
• Membrane Transport Proteins genetics   metabolism   MeSH
• Arabidopsis Proteins * genetics   metabolism   MeSH
• Intrinsically Disordered Proteins * genetics   metabolism   MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Indoleacetic Acids MeSH
• Membrane Transport Proteins MeSH
• PIN1 protein, Arabidopsis MeSH Browser
• Arabidopsis Proteins * MeSH
• Intrinsically Disordered Proteins * MeSH

Brassica napus (rapeseed) is the second most important oilseed crop worldwide. Global rise in average ambient temperature and extreme weather severely impact rapeseed seed yield. However, fewer research explained the phenotype changes caused by moderate-to-high temperatures in rapeseed. To investigate these events, we determined the long-term response of three spring cultivars to different temperature regimes (21/18°C, 28/18°C, and 34/18°C) mimicking natural temperature variations. The analysis focused on the plant appearance, seed yield, quality and viability, and embryo development. Our microscopic observations suggest that embryonic development is accelerated and defective in high temperatures. Reduced viable seed yield at warm ambient temperature is due to a reduced fertilization rate, increased abortion rate, defective embryonic development, and pre-harvest sprouting. Reduced auxin levels in young seeds and low ABA and auxin levels in mature seeds may cause embryo pattern defects and reduced seed dormancy, respectively. Glucosinolates and oil composition measurements suggest reduced seed quality. These identified cues help understand seed thermomorphogenesis and pave the way to developing thermoresilient rapeseed.

• Keywords
• Brassica napus, embryo development, high temperatures, hormonal profiling, oil content, seed development, thermomorphogenesis,
• Publication type
• Journal Article MeSH

Embryogenesis in seed plants is the process during which a single cell develops into a mature multicellular embryo that encloses all the modules and primary patterns necessary to build the architecture of the new plant after germination. This process involves a series of cell divisions and coordinated cell fate determinations resulting in the formation of an embryonic pattern with a shoot-root axis and cotyledon(s). The phytohormone auxin profoundly controls pattern formation during embryogenesis. Auxin functions in the embryo through its maxima/minima distribution, which acts as an instructive signal for tissue specification and organ initiation. In this review, we describe how disruptions of auxin biosynthesis, transport, and response severely affect embryo development. Also, the mechanism of auxin action in the development of the shoot-root axis and the three-tissue system is discussed with recent findings. Biological tools that can be implemented to study the auxin function during embryo development are presented, as they may be of interest to the reader.

• MeSH
• Biological Transport MeSH
• Plant Roots growth & development   MeSH
• Indoleacetic Acids metabolism   MeSH
• Plant Growth Regulators metabolism   MeSH
• Seeds growth & development   MeSH
• Signal Transduction MeSH
• Plant Shoots growth & development   MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Review MeSH
• Names of Substances
• Indoleacetic Acids MeSH
• Plant Growth Regulators MeSH

• Publication type
• Journal Article MeSH

Eukaryotic cells rely on the accuracy and efficiency of vesicular traffic. In plants, disturbances in vesicular trafficking are well studied in quickly dividing root meristem cells or polar growing root hairs and pollen tubes. The development of the female gametophyte, a unique haploid reproductive structure located in the ovule, has received far less attention in studies of vesicular transport. Key molecules providing the specificity of vesicle formation and its subsequent recognition and fusion with the acceptor membrane are Rab proteins. Rabs are anchored to membranes by covalently linked geranylgeranyl group(s) that are added by the Rab geranylgeranyl transferase (RGT) enzyme. Here we show that Arabidopsis plants carrying mutations in the gene encoding the β-subunit of RGT (rgtb1) exhibit severely disrupted female gametogenesis and this effect is of sporophytic origin. Mutations in rgtb1 lead to internalization of the PIN1 and PIN3 proteins from the basal membranes to vesicles in provascular cells of the funiculus. Decreased transport of auxin out of the ovule is accompanied by auxin accumulation in tissue surrounding the growing gametophyte. In addition, female gametophyte development arrests at the uni- or binuclear stage in a significant portion of the rgtb1 ovules. These observations suggest that communication between the sporophyte and the developing female gametophyte relies on Rab-dependent vesicular traffic of the PIN1 and PIN3 transporters and auxin efflux out of the ovule.

• Keywords
• Arabidopsis, PIN1, PIN3, Rab, auxin transport, female gametophyte, funiculus, ovule, rab geranylgeranyl transferase,
• MeSH
• Arabidopsis * genetics   MeSH
• Indoleacetic Acids MeSH
• Arabidopsis Proteins * genetics   MeSH
• Pollen Tube MeSH
• Ovule genetics   MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Indoleacetic Acids MeSH
• Arabidopsis Proteins * MeSH

Directional transport of the phytohormone auxin is a versatile, plant-specific mechanism regulating many aspects of plant development. The recently identified plant hormones, strigolactones (SLs), are implicated in many plant traits; among others, they modify the phenotypic output of PIN-FORMED (PIN) auxin transporters for fine-tuning of growth and developmental responses. Here, we show in pea and Arabidopsis that SLs target processes dependent on the canalization of auxin flow, which involves auxin feedback on PIN subcellular distribution. D14 receptor- and MAX2 F-box-mediated SL signaling inhibits the formation of auxin-conducting channels after wounding or from artificial auxin sources, during vasculature de novo formation and regeneration. At the cellular level, SLs interfere with auxin effects on PIN polar targeting, constitutive PIN trafficking as well as clathrin-mediated endocytosis. Our results identify a non-transcriptional mechanism of SL action, uncoupling auxin feedback on PIN polarity and trafficking, thereby regulating vascular tissue formation and regeneration.

• MeSH
• Arabidopsis genetics   metabolism   MeSH
• Heterocyclic Compounds, 3-Ring metabolism   MeSH
• Pisum sativum genetics   metabolism   MeSH
• Indoleacetic Acids metabolism   MeSH
• Lactones metabolism   MeSH
• Arabidopsis Proteins genetics   metabolism   MeSH
• Gene Expression Regulation, Plant genetics   physiology   MeSH
• Plant Growth Regulators metabolism   MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• GR24 strigolactone MeSH Browser
• Heterocyclic Compounds, 3-Ring MeSH
• Indoleacetic Acids MeSH
• Lactones MeSH
• Arabidopsis Proteins MeSH
• Plant Growth Regulators MeSH

The fine tuning of hormone (e.g., auxin and gibberellin) levels and hormone signaling is required for maintaining normal embryogenesis. Embryo polarity, for example, is ensured by the directional movement of auxin that is controlled by various types of auxin transporters. Here, we present pieces of evidence for the auxin-gibberellic acid (GA) hormonal crosstalk during embryo development and the regulatory role of the Arabidopsis thaliana Calcium-Dependent Protein Kinase-Related Kinase 5 (AtCRK5) in this regard. It is pointed out that the embryogenesis of the Atcrk5-1 mutant is delayed in comparison to the wild type. This delay is accompanied with a decrease in the levels of GA and auxin, as well as the abundance of the polar auxin transport (PAT) proteins PIN1, PIN4, and PIN7 in the mutant embryos. We have previously showed that AtCRK5 can regulate the PIN2 and PIN3 proteins either directly by phosphorylation or indirectly affecting the GA level during the root gravitropic and hypocotyl hook bending responses. In this manuscript, we provide evidence that the AtCRK5 protein kinase can in vitro phosphorylate the hydrophilic loops of additional PIN proteins that are important for embryogenesis. We propose that AtCRK5 can govern embryo development in Arabidopsis through the fine tuning of auxin-GA level and the accumulation of certain polar auxin transport proteins.

• Keywords
• Arabidopsis thaliana, Calcium-Dependent Protein Kinase-Related Kinase (CRK), GA3, auxin gradient, embryogenesis, polar auxin transport (PAT) proteins,
• MeSH
• Arabidopsis growth & development   metabolism   MeSH
• Enzyme-Linked Immunosorbent Assay MeSH
• Gibberellins analysis   metabolism   MeSH
• Germination * MeSH
• Indoleacetic Acids metabolism   MeSH
• Membrane Transport Proteins genetics   metabolism   MeSH
• Protein Serine-Threonine Kinases metabolism   MeSH
• Arabidopsis Proteins genetics   metabolism   MeSH
• Receptors, Cell Surface metabolism   MeSH
• Gene Expression Regulation, Plant MeSH
• Seeds anatomy & histology   growth & development   metabolism   MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• CRK5 protein, Arabidopsis MeSH Browser
• gibberellic acid MeSH Browser
• Gibberellins MeSH
• Indoleacetic Acids MeSH
• Membrane Transport Proteins MeSH
• Protein Serine-Threonine Kinases MeSH
• Arabidopsis Proteins MeSH
• Receptors, Cell Surface MeSH

The plant-specific proteins named PIN-FORMED (PIN) efflux carriers facilitate the direction of auxin flow and thus play a vital role in the establishment of local auxin maxima within plant tissues that subsequently guide plant ontogenesis. They are membrane integral proteins with two hydrophobic regions consisting of alpha-helices linked with a hydrophilic loop, which is usually longer for the plasma membrane-localized PINs. The hydrophilic loop harbors molecular cues important for the subcellular localization and thus auxin efflux function of those transporters. The three-dimensional structure of PIN has not been solved yet. However, there are scattered but substantial data concerning the functional characterization of amino acid strings that constitute these carriers. These sequences include motifs vital for vesicular trafficking, residues regulating membrane diffusion, cellular polar localization, and activity of PINs. Here, we summarize those bits of information striving to provide a reference to structural motifs that have been investigated experimentally hoping to stimulate the efforts toward unraveling of PIN structure-function connections.

• Keywords
• PIN efflux carriers, auxin transport, protein domains, sequence motifs, subcellular trafficking,
• Publication type
• Journal Article MeSH
• Review MeSH