The transcription factors BEL1 and SPL are required for cytokinin and auxin signaling during ovule development in Arabidopsis

Hormones, such as auxin and cytokinin, are involved in the complex molecular network that regulates the coordinated development of plant organs. Genes controlling ovule patterning have been identified and studied in detail; however, the roles of auxin and cytokinin in ovule development are largely unknown. Here we show that key cytokinin pathway genes, such as isopentenyltransferase and cytokinin receptors, are expressed during ovule development. Also, in a cre1-12 ahk2-2 ahk3-3 triple mutant with severely reduced cytokinin perception, expression of the auxin efflux facilitator PIN-FORMED 1 (PIN1) was severely reduced. In sporocyteless/nozzle (spl/nzz) mutants, which show a similar phenotype to the cre1-12 ahk2-2 ahk3-3 triple mutant, PIN1 expression is also reduced. Treatment with the exogenous cytokinin N-6-benzylaminopurine also altered both auxin distribution and patterning of the ovule; this process required the homeodomain transcription factor BELL1 (BEL1). Thus, this article shows that cytokinin regulates ovule development through the regulation of PIN1. Furthermore, the transcription factors BEL1 and SPL/NZZ, previously described as key regulators of ovule development, are needed for the auxin and cytokinin signaling pathways for the correct patterning of the ovule

A paternal signal induces endosperm proliferation upon fertilization in Arabidopsis

In multicellular organisms, sexual reproduction relies on the formation of highly differentiated cells, the gametes, which await fertilization in a quiescent state. Upon fertilization, the cell cycle resumes. Successful development requires that male and female gametes are in the same phase of the cell cycle. The molecular mechanisms that reinstate cell division in a fertilization-dependent manner are poorly understood in both animals and plants. Using Arabidopsis, we show that a sperm-derived signal induces the proliferation of a female gamete, the central cell, precisely upon fertilization. The central cell is arrested in S phase by the activity of the RETINOBLASTOMA RELATED1 (RBR1) protein. Upon fertilization, delivery of the core cell cycle component CYCD7;1 causes RBR1 degradation and thus S phase progression, ensuring the formation of functional endosperm and, consequently, viable seeds

A molecular framework controlling style morphology in Brassicaceae

Organ formation in multicellular organisms depends on the coordinated activities of regulatory components that integrate developmental and hormonal cues to control gene expression and mediate cell-type specification. For example, development of the Arabidopsis gynoecium is tightly controlled by distribution and synthesis of the plant hormone auxin. The functions of several transcription factors (TFs) have been linked with auxin dynamics during gynoecium development; yet how their activities are coordinated is not known. Here, we show that five such TFs function together to ensure polarity establishment at the gynoecium apex. The auxin response factor ETTIN (ARF3; herein, ETT) is a central component of this framework. Interaction of ETT with TF partners is sensitive to the presence of auxin and our results suggest that ETT forms part of a repressive gene-regulatory complex. We show that this function is conserved between members of the Brassicaceae family and that variation in an ETT subdomain affects interaction strengths and gynoecium morphology. These results suggest that variation in affinities between conserved TFs can lead to morphological differences and thus contribute to the evolution of diverse organ shapes

Auxin-Induced Modulation of ETTIN Activity Orchestrates Gene Expression in Arabidopsis

The phytohormone auxin governs crucial developmental decisions throughout the plant life cycle. Auxin signaling is effectuated by auxin response factors (ARFs) whose activity is repressed by Aux/IAA proteins under low auxin levels, but relieved from repression when cellular auxin concentrations increase. ARF3/ETTIN (ETT) is a conserved noncanonical Arabidopsis thaliana ARF that adopts an alternative auxin-sensing mode of translating auxin levels into multiple transcriptional outcomes. However, a mechanistic model for how this auxin-dependent modulation of ETT activity regulates gene expression has not yet been elucidated. Here, we take a genome-wide approach to show how ETT controls developmental processes in the Arabidopsis shoot through its auxin-sensing property. Moreover, analysis of direct ETT targets suggests that ETT functions as a central node in coordinating auxin dynamics and plant development and reveals tight feedback regulation at both the transcriptional and protein-interaction levels. Finally, we present an example to demonstrate how auxin sensitivity of ETT-protein interactions can shape the composition of downstream transcriptomes to ensure specific developmental outcomes. These results show that direct effects of auxin on protein factors, such as ETT-TF complexes, comprise an important part of auxin biology and likely contribute to the vast number of biological processes affected by this simple molecule

Level of Awareness and Attitudes towards Plastic Contamination by Students of an Italian University

Although micro- and nanoplastics (MNPs) represent one of the main environmental emergencies worldwide, citizens are not always aware of their active role in contributing to such contamination. In this study, the perception, level of knowledge, and behaviours towards MNPs were assessed in young citizens in Modena (Italy), represented by science-oriented Bachelor’s students (n = 220) enrolled at the university, through the administration of a voluntary-based questionnaire. No differences in knowledge and in students’ attitudes were observed according to gender and the undergraduate program. Students seem to be aware of MNPs’ global distribution and effects on ecosystems but were less advised about MNP types and their potential effects on human health. A positive correlation between the students’ level of concern and their knowledge or their behaviour was found. Differently, no correlation between students’ knowledge and behaviour towards plastic and MNP contamination was observed. Thus, having a good knowledge of the issue does not always translate into effective actions planned to mitigate the problem. As a first step forward, more environmental education programs should be promoted to increase knowledge and awareness in young citizen as well as pro-environmental behaviours to pursue future mitigation strategies

Bearded versus thorny: The fireworm Hermodice carunculata preys on the sea urchin Paracentrotus lividus

The bearded fireworm, Hermodice carunculata (Polychaeta: Amphinomidae) has rapidly increased in abundance in Mediterranean infralittoral rocky habitats. We have recently observed the bearded fireworm preying on the sea urchin Paracentrotus lividus, which is a major determinant of algal community structure in this system. To document the full sequence of behaviors in an attack, we observed interactions between H. carunculata and P. lividus under controlled conditions in the lab. Upon a fortuitous contact, a fireworm rapidly initiated an attack on the urchin, everting its pharynx over it and starting to suck and ingest the spines. The attack forced the detachment of the urchin from the substrate and the exposure of its oral side. Then, the fireworm moved toward the urchin mouth, placed its buccal mass over the Aristotle's lantern (the large powerful urchin “jaw”), removed it with a suction generated by the pharyngeal musculature and entered the test. When an increase in P. lividus mortality caused by predation occurs, a top–down control of communities may take place, triggering different habitat formation (algal forest vs. barren). Further research on the effects of the predation of the bearded fireworm on urchin populations is required to assess their potential repercussions for the structure and functioning of Mediterranean rocky reef ecosystem

Novel Natural Compounds and Their Anatomical Distribution in the Stinging Fireworm Hermodice carunculata (Annelida)

Increasing evidence in the field of bioprospection fosters the necessity of studying poorly investigated poisonous marine invertebrates to expand knowledge on animal venom biology. Among marine annelids, amphinomid fireworms are notorious for their bearded trunk equipped with a powerful stinging capacity. Here, a methodological workflow based on analytical chemistry techniques (compound isolation followed by mass spectrometry and spectroscopy analyses) was applied to gain new insights, leading to the identification and structural elucidation of an array of natural products from Mediterranean specimens of Hermodice carunculata. Eight betaine-derived unprecedented compounds, named "carunculines", were detected, bearing two terminal ammonium groups tri-and disubstituted at the Cα (A, B) and a series of different alkyl chains (I-VIII). The mixture of chemicals was found in all the body parts of H. carunculata, supporting a mechanism of action triggered by their vehiculation inside the dorsal chaetae, and subsequent injection when chaetae break off on contact. Preliminary investigations to understand adaptive features were also performed, showing a trend in carunculine abundance that fits into the evolutionary history of these worms. These findings shed light on the chemical ecology of amphinomids, giving reasons for the success of H. carunculata in benthic environments and providing promising novel metabolites for biotechnological implications