Plant glutamate receptor-like (GLR) genes encode ion channels with demonstrated roles in electrical and calcium (Ca²⁺) signaling. The expansion of the GLR family along the lineage of land plants, culminating in the appearance of a multiclade system among flowering plants, has been a topic of interest since their discovery nearly 25 years ago. GLRs are involved in many physiological processes, from wound signaling to transcriptional regulation to sexual reproduction. Emerging evidence supports the notion that their fundamental functions are conserved among different groups of plants as well. In this review, we update the physiological and genetic evidence for GLRs, establishing their role in signaling and cell–cell communication. Special emphasis is given to the recent discussion of GLRs’ atomic structures. Along with functional assays, a structural view of GLRs’ molecular organization presents a window for novel hypotheses regarding the molecular mechanisms underpinning signaling associated with the ionic fluxes that GLRs regulate. Newly uncovered transcriptional regulations associated with GLRs—which propose the involvement of genes from all clades ofArabidopsis thaliana in ways not previously observed—are discussed in the context of the broader impacts of GLR activity. We posit that the functions of GLRs in plant biology are probably much broader than anticipated, but describing their widespread involvement will only be possible with (a) a comprehensive understanding of the channel's properties at the molecular and structural levels, including protein–protein interactions, and (b) the design of new genetic approaches to explore stress and pathogen responses where precise transcriptional control may result in more precise testable hypotheses to overcome their apparent functional redundancies.

The establishment, maintenance, and removal of epigenetic modifications provide an additional layer of regulation, beyond genetically encoded factors, by which plants can control developmental processes and adapt to the environment. Epigenetic inheritance, while historically referring to information not encoded in the DNA sequence that is inherited between generations, can also refer to epigenetic modifications that are maintained within an individual but are reset between generations. Both types of epigenetic inheritance occur in plants, and the functions and mechanisms distinguishing the two are of great interest to the field. Here, we discuss examples of epigenetic dynamics and maintenance during selected stages of growth and development and their functional consequences. Epigenetic states are also dynamic in response to stress, with consequences for transposable element regulation. How epigenetic resetting between generations occurs during normal development and in response to stress is an emerging area of research.

cis-Regulatory elements encode the genomic blueprints that ensure the proper spatiotemporal patterning of gene expression necessary for appropriate development and responses to the environment. Accumulating evidence implicates changes to gene expression as a major source of phenotypic novelty in eukaryotes, including acute phenotypes such as disease and cancer in mammals. Moreover, genetic and epigenetic variation affecting cis-regulatory sequences over longer evolutionary timescales has become a recurring theme in studies of morphological divergence and local adaptation. Here, we discuss the functions of and methods used to identify various classes of cis-regulatory elements, as well as their role in plant development and response to the environment. We highlight opportunities to exploit cis-regulatory variants underlying plant development and environmental responses for crop improvement efforts. Although a comprehensive understanding of cis-regulatory mechanisms in plants has lagged behind that in animals, we showcase several breakthrough findings that have profoundly influenced plant biology and shaped the overall understanding of transcriptional regulation in eukaryotes.

Plants’ ability to chemically modify core structures of specialized metabolites is the main reason why the plant kingdom contains such a wide and rich array of diverse compounds. One of the most important types of chemical modifications of small molecules is the addition of an acyl moiety to produce esters and amides. Large-scale phylogenomics analyses have shown that the enzymes that perform acyl transfer reactions on the myriad small molecules synthesized by plants belong to only a few gene families. This review is focused on describing the biochemistry, evolutionary origins, and chemical ecology implications of one of these families—the BAHD acyltransferases. The growth of advanced metabolomic studies coupled with next-generation sequencing of diverse plant species has confirmed that the BAHD family plays critical roles in modifying nearly all known classes of specialized metabolites. The current and future outlook for research on BAHDs includes expanding their roles in synthetic biology and metabolic engineering.

SWITCH deficient SUCROSE NONFERMENTING (SWI/SNF) class chromatin remodeling complexes (CRCs) use the energy derived from ATP hydrolysis to facilitate access of proteins to the genomic DNA for transcription, replication, and DNA repair. Uniquely, SWI/SNF CRCs can both slide the histone octamer along the DNA or eject it from the DNA. Given their ability to change the chromatin status quo, SWI/SNF remodelers are critical for cell fate reprogramming with pioneer and other transcription factors, for responses to environmental challenges, and for disease prevention. Recent cryo-electron microscopy and mass spectrometry approaches have uncovered different subtypes of SWI/SNF complexes with unique properties and functions. At the same time, tethering or rapid depletion and inactivation of SWI/SNF have provided novel insight into SWI/SNF requirements for enhancer activity and into balancing chromatin compaction and accessibility in concert with Polycomb complexes. Given their importance, SWI/SNF recruitment to genomic locations by transcription factors and their biochemical activity is tightly controlled. This review focuses on recent advances in our understanding of SWI/SNF CRCs in animals and plants and discusses the multiple nuclear and biological roles of SWI/SNF CRCs and how SWI/SNF activity is altered by complex subunit composition, posttranslational modifications, and the chromatin context to support proper development and response to extrinsic cues.

Photoperiod-measuring mechanisms allow organisms to anticipate seasonal changes to align reproduction and growth with appropriate times of the year. This review provides historical and modern context to studies of plant photoperiodism. We describe how studies of photoperiodic flowering in plants led to the first theoretical models of photoperiod-measuring mechanisms in any organism. We discuss how more recent molecular genetic studies in Arabidopsis and rice have revisited these concepts. We then discuss how photoperiod transcriptomics provides new lessons about photoperiodic gene regulatory networks and the discovery of noncanonical photoperiod-measuring systems housed in metabolic networks of plants. This leads to an examination of nonflowering developmental processes controlled by photoperiod, including metabolism and growth. Finally, we highlight the importance of understanding photoperiodism in the context of climate change, delving into the rapid latitudinal migration of plant species and the potential role of photoperiod-measuring systems in generating photic barriers during migration.

Lipid droplets, also known as oil bodies or lipid bodies, are plant organelles that compartmentalize neutral lipids as a hydrophobic matrix covered by proteins embedded in a phospholipid monolayer. Some of these proteins have been known for decades, such as oleosins, caleosins, and steroleosins, whereas a host of others have been discovered more recently with various levels of abundance on lipid droplets, depending on the tissue and developmental stage. In addition to a growing inventory of lipid droplet proteins, the subcellular machinery that contributes to the biogenesis and degradation of lipid droplets is being identified and attention is turning to more mechanistic questions regarding lipid droplet dynamics. While lipid droplets are mostly regarded as storage deposits for carbon and energy in lipid-rich plant tissues such as seeds, these organelles are present in essentially all plant cells, where they display additional functions in signaling, membrane remodeling, and the compartmentalization of a variety of hydrophobic components. Remarkable metabolic engineering efforts have demonstrated the plasticity of vegetative tissues such as leaves to synthesize and package large amounts of storage lipids, which enable future applications in bioenergy and the engineering of high-value lipophilic compounds. Here, we review the growing body of knowledge about lipid droplets in plant cells, describe the evolutionary similarity and divergence in their associated subcellular machinery, and point to gaps that deserve future attention.

Plant volatiles comprise thousands of molecules from multiple metabolic pathways, distinguished by sufficient vapor pressure to evaporate into the headspace under normal environmental conditions. Many are implicated as ecological signals, but what is the evidence—and how do they work? Volatiles diffuse, are carried by wind, and may be taken up by other organisms or degrade with exposure to atmospheric ozone, radicals, and UV light; visual signals such as color are not subject to these complications (but require a line of sight). Distantly related plants—and nonplants—produce many of the same volatiles, yet specific compounds and blends may be distinct. Here, I present a quantitative review of the literature on plant volatiles as ecological signals, illustrating a field that has focused on developing ideas as much as reporting primary data. I discuss advantages and constraints, review recent advances, and propose considerations for primary studies to elucidate particular functions of plant volatiles.

The aboveground parts of terrestrial plants are colonized by a variety of microbes that collectively constitute the phyllosphere microbiota. Decades of pioneering work using individual phyllosphere microbes, including commensals and pathogens, have provided foundational knowledge about how individual microbes adapt to the phyllosphere environment and their role in providing biological control against pathogens. Recent studies have revealed a more complete repertoire of phyllosphere microbiota across plant taxa and how plants respond to and regulate the level and composition of phyllosphere microbiota. Importantly, the development of several gnotobiotic systems is allowing causative and mechanistic studies to determine the contributions of microbiota to phyllosphere health and productivity. New insights into how the phyllosphere carries out key biological processes, including photosynthesis, biomass accumulation, reproduction, and defense against biotic and abiotic insults, in either the presence or absence of a normal microbiota could unleash novel plant- and microbiota-based technologies to improve agriculturally relevant traits of crop plants.

Plant cells accumulate small RNA molecules that regulate plant development, genome stability, and environmental responses. These small RNAs fall into three major classes based on their function and mechanisms of biogenesis—microRNAs, heterochromatic small interfering RNAs, and secondary small interfering RNAs—plus several other less well-characterized categories. Biogenesis of each small RNA class requires a pathway of factors, some specific to each pathway and others involved in multiple pathways. Diverse sequenced plant genomes, along with rapid developments in sequencing, imaging, and genetic transformation techniques, have enabled significant progress in understanding the biogenesis, functions, and evolution of plant small RNAs, including those that had been poorly characterized because they were absent or had low representation in Arabidopsis (Arabidopsis thaliana). Here, we review recent findings about plant small RNAs and discuss our current understanding of their biogenesis mechanisms, targets, modes of action, mobility, and functions in Arabidopsis and other plant species, including economically important crops.