HEXOKINASE1 forms a nuclear complex with the PRC2 subunits CURLY LEAF and SWINGER to regulate glucose signaling

Telo boxes within the AGAMOUS second intron recruit histone 3 lysine 27 methylation to increase petal number in rose (Rosa chinensis) in response to low temperatures

The petals of rose (Rosa sp.) flowers determine the ornamental and industrial worth of this species. The number of petals in roses was previously shown to be subject to fluctuations in ambient temperature. However, the mechanisms by which rose detects and responds to temperature changes are not entirely understood. In this study, we identified short interstitial telomere motifs (telo boxes) in the second intron of AGAMOUS (RcAG) from China rose (Rosa chinensis) that play an essential role in precise temperature perception. The second intron of RcAG harbors two telo boxes that recruit telomere repeat binding factors (RcTRBs), which interact with CURLY LEAF (RcCLF) to compose a repressor complex. We show that this complex suppresses RcAG expression when plants are subjected to low temperatures via depositing H3K27me3 marks (trimethylation of lysine 27 on histone H3) over the RcAG gene body. This regulatory mechanism explains the low-temperature-dependent decrease in RcAG transcript levels, leading to the production of more petals under these conditions. Our results underscore an interesting intron-mediated regulatory mechanism governing RcAG expression, enabling rose plants to perceive temperature cues and establish petal numbers.

The critical roles of three sugar-related proteins (HXK, SnRK1, TOR) in regulating plant growth and stress responses

Sugar signaling is one of the most critical regulatory signals in plants, and its metabolic network contains multiple regulatory factors. Sugar signal molecules regulate cellular activities and organism development by combining with other intrinsic regulatory factors and environmental inputs. HXK, SnRK1, and TOR are three fundamental proteins that have a pivotal role in the metabolism of sugars in plants. HXK, being the initial glucose sensor discovered in plants, is renowned for its multifaceted characteristics. Recent investigations have unveiled that HXK additionally assumes a significant role in plant hormonal signaling and abiotic stress. SnRK1 serves as a vital regulator of growth under energy-depleted circumstances, whereas TOR, a large protein, acts as a central integrator of signaling pathways that govern cell metabolism, organ development, and transcriptome reprogramming in response to diverse stimuli. Together, these two proteins work to sense upstream signals and modulate downstream signals to regulate cell growth and proliferation. In recent years, there has been an increasing amount of research on these three proteins, particularly on TOR and SnRK1. Furthermore, studies have found that these three proteins not only regulate sugar signaling but also exhibit certain signal crosstalk in regulating plant growth and development. This review provides a comprehensive overview and summary of the basic functions and regulatory networks of these three proteins. It aims to serve as a reference for further exploration of the interactions between these three proteins and their involvement in co-regulatory networks.

Active oxygen generation induced by the glucose sensor TaHXK7-1A decreased the drought resistance of transgenic Arabidopsis and wheat (Triticum aestivum L.)

Improving wheat drought resistance is of great significance for grain production and food security. Hexokinases (HXKs) play a role in sugar signal transduction and are involved in abiotic stress responses in wheat. To clarify the relationship between HXKs and drought stress in wheat, we used the rice active oxygen induction gene OsHXK1 as a reference sequence and the homologously cloned wheat TaHXK7-1A gene. TaHXK7-1A was localized in the nucleus and cell membrane. Under drought stress, over-expression of TaHXK7-1A increased the contents of O2·－ and malondialdehyde (MDA) and significantly up-regulated the respiratory burst oxidative homologue (RBOHs) genes in transgenic Arabidopsis. In addition, the over-expression of TaHXK7-1A inhibited the growth of Arabidopsis seedlings and increased ROS accumulation under 6 % exogenous glucose treatment. Gene silencing of TaHXK7-1 decreased the contents of O2·－ and MDA in wheat leaves under drought stress, and the RBOHs was significantly down-regulated, which improved the drought resistance of wheat. The results of yeast one-hybrid, EMSA, and dual-luciferase assays showed that TabHLH148-5A bound to the E-box motif of the TaHXK7-1A promoter and inhibited the expression of TaHXK7-1A. In addition, yeast two-hybrid and luciferase complementation imaging assays showed that TaHXK7-1A interacted with TaGRF3-4A. These results indicate that the glucose sensor TaHXK7-1A was negatively regulated by TabHLH148-5A, interacted with TaGRF3-4A, and negatively regulated wheat drought resistance by regulating RBOHs expression and inducing ROS production, thus providing a theoretical basis for revealing the molecular mechanism of wheat drought resistance.

A Mitochondrial Localized Chaperone Regulator OsBAG6 Functions in Saline-Alkaline Stress Tolerance in Rice

B-cell lymphoma 2 (Bcl-2)-associated athanogene (BAG) family genes play prominent roles in regulating plant growth, development, and stress response. Although the molecular mechanism underlying BAG's response to abiotic stress has been studied in Arabidopsis, the function of OsBAG underlying saline-alkaline stress tolerance in rice remains unclear. In this study, OsBAG6, a chaperone regulator localized to mitochondria, was identified as a novel negative regulator of saline-alkaline stress tolerance in rice. The expression level of OsBAG6 was induced by high concentration of salt, high pH, heat and abscisic acid treatments. Overexpression of OsBAG6 in rice resulted in significantly reduced plant heights, grain size, grain weight, as well as higher sensitivity to saline-alkaline stress. By contrast, the osbag6 loss-of-function mutants exhibited decreased sensitivity to saline-alkaline stress. The transcriptomic analysis uncovered differentially expressed genes related to the function of "response to oxidative stress", "defense response", and "secondary metabolite biosynthetic process" in the shoots and roots of OsBAG6-overexpressing transgenic lines. Furthermore, cytoplasmic levels of Ca2+ increase rapidly in plants exposed to saline-alkaline stress. OsBAG6 bound to calcium sensor OsCaM1-1 under normal conditions, which was identified by comparative interactomics, but not in the presence of elevated Ca2+. Released OsCaM1-1 saturated with Ca2+ is then able to regulate downstream stress-responsive genes as part of the response to saline-alkaline stress. OsBAG6 also interacted with energy biosynthesis and metabolic pathway proteins that are involved in plant growth and saline-alkaline stress response mechanisms. This study reveals a novel function for mitochondrial localized OsBAG6 proteins in the saline-alkaline stress response alongside OsCaM1-1.

How metabolism and development are intertwined in space and time

Developmental transitions, occurring throughout the life cycle of plants, require precise regulation of metabolic processes to generate the energy and resources necessary for the committed growth processes. In parallel, the establishment of new cells, tissues, and even organs, alongside their differentiation provoke profound changes in metabolism. It is increasingly being recognized that there is a certain degree of feedback regulation between the components and products of metabolic pathways and developmental regulators. The generation of large-scale metabolomics datasets during developmental transitions, in combination with molecular genetic approaches has helped to further our knowledge on the functional importance of metabolic regulation of development. In this perspective article, we provide insights into studies that elucidate interactions between metabolism and development at the temporal and spatial scales. We additionally discuss how this influences cell growth-related processes. We also highlight how metabolic intermediates function as signaling molecules to direct plant development in response to changing internal and external conditions.

Dynamics of epigenetic control in plants via SET domain containing proteins: Structural and functional insights

Plants control expression of their genes in a way that involves manipulating the chromatin structural dynamics in order to adapt to environmental changes and carry out developmental processes. Histone modifications like histone methylation are significant epigenetic marks which profoundly and globally modify chromatin, potentially affecting the expression of several genes. Methylation of histones is catalyzed by histone lysine methyltransferases (HKMTs), that features an evolutionary conserved domain known as SET [Su(var)3-9, E(Z), Trithorax]. This methylation is directed at particular lysine (K) residues on H3 or H4 histone. Plant SET domain group (SDG) proteins are categorized into different classes that have been conserved through evolution, and each class have specificity that influences how the chromatin structure operates. The domains discovered in plant SET domain proteins have typically been linked to protein-protein interactions, suggesting that majority of the SDGs function in complexes. Additionally, SDG-mediated histone mark deposition also affects alternative splicing events. In present review, we discussed the diversity of SDGs in plants including their structural properties. Additionally, we have provided comprehensive summary of the functions of the SDG-domain containing proteins in plant developmental processes and response to environmental stimuli have also been highlighted.

Complex genetic architecture underlying the plasticity of maize agronomic traits

Phenotypic plasticity is the ability of a given genotype to produce multiple phenotypes in response to changing environmental conditions. Understanding the genetic basis of phenotypic plasticity and establishing a predictive model is highly relevant to future agriculture under a changing climate. Here we report findings on the genetic basis of phenotypic plasticity for 23 complex traits using a diverse maize population planted at five sites with distinct environmental conditions. We found that latitude-related environmental factors were the main drivers of across-site variation in flowering time traits but not in plant architecture or yield traits. For the 23 traits, we detected 109 quantitative trait loci (QTLs), 29 for mean values, 66 for plasticity, and 14 for both parameters, and 80% of the QTLs interacted with latitude. The effects of several QTLs changed in magnitude or sign, driving variation in phenotypic plasticity. We experimentally validated one plastic gene, ZmTPS14.1, whose effect was likely mediated by the compensation effect of ZmSPL6 from a downstream pathway. By integrating genetic diversity, environmental variation, and their interaction into a joint model, we could provide site-specific predictions with increased accuracy by as much as 9.9%, 2.2%, and 2.6% for days to tassel, plant height, and ear weight, respectively. This study revealed a complex genetic architecture involving multiple alleles, pleiotropy, and genotype-by-environment interaction that underlies variation in the mean and plasticity of maize complex traits. It provides novel insights into the dynamic genetic architecture of agronomic traits in response to changing environments, paving a practical way toward precision agriculture.

Hexokinase1: A glucose sensor involved in drought stress response and sugar metabolism depending on its kinase activity in strawberry

Hexokinase1 (HXK1) is a bifunctional enzyme that plays indispensable roles in plant growth, nitrogen utilization, and stress resistance. However, information on the HXK family members of strawberries and their functions in glucose sensing and metabolic regulation is scarce. In the present study, four HXKs were firstly identified in the genome of Fragaria vesca and F. pentaphylla. The conserved domains of the HXK1s were confirmed, and a site-directed mutation (S177A) was introduced into the FpHXK1. FpHXK1, which shares the highest identity with the AtHXK1 was able to restore the glucose sensitivity and developmental defects of the Arabidopsis gin2-1 mutant, but not its kinase-activity-impaired mutant (FpHXK1^S177A ). The transcription of FpHXK1 was dramatically up-regulated under PEG-simulated drought stress conditions. The inhibition of the HXK kinase activity delayed the strawberry plant's responses to drought stress. Transient overexpression of the FpHXK1 and its kinase-impaired mutant differentially affected the level of glucose, sucrose, anthocyanins, and total phenols in strawberry fruits. All these results indicated that the FpHXK1, acting as a glucose sensor, was involved in drought stress response and sugar metabolism depending on its kinase activity.

Dynamic regulation of DNA methylation and histone modifications in response to abiotic stresses in plants

DNA methylation and histone modification are evolutionarily conserved epigenetic modifications that are crucial for the expression regulation of abiotic stress-responsive genes in plants. Dynamic changes in gene expression levels can result from changes in DNA methylation and histone modifications. In the last two decades, how epigenetic machinery regulates abiotic stress responses in plants has been extensively studied. Here, based on recent publications, we review how DNA methylation and histone modifications impact gene expression regulation in response to abiotic stresses such as drought, abscisic acid, high salt, extreme temperature, nutrient deficiency or toxicity, and ultraviolet B exposure. We also review the roles of epigenetic mechanisms in the formation of transgenerational stress memory. We posit that a better understanding of the epigenetic underpinnings of abiotic stress responses in plants may facilitate the design of more stress-resistant or -resilient crops, which is essential for coping with global warming and extreme environments.