Brassinosteroid-lipid membrane interaction under low and high temperature stress in model systems

Integrated Analyses Reveal the Physiological and Molecular Mechanisms of Brassinolide in Modulating Salt Tolerance in Rice

Salt stress poses a significant threat to crop growth. While brassinolide (BR) has been shown to alleviate its adverse effects and modulate plant development, the precise mechanism underlying BR-induced salt tolerance in rice remains unclear. In this study, the Chaoyouqianhao and Huanghuazhan rice varieties were employed to investigate the effects of BR seed soaking on the seedling phenotype, physiology, transcriptome, and metabolome under salt stress. The results demonstrated that BR treatment significantly enhanced rice plant height, root length, biomass, and antioxidant enzyme activities, while reducing leaf membrane damage, promoting ion homeostasis, and improving the photosynthetic capacity and salt tolerance. The transcriptome analysis revealed that BR regulated the expression of 1042 and 826 genes linked to antioxidant activity, ion homeostasis, photosynthesis, and lipid metabolism under salt stress. These included genes involved in Na+ efflux (OsNCED2, OsHKT2;1, and OsHKT1;1), photosynthetic electron transport (OsFd5 and OsFdC1), photosystem II (OsPsbR1, OsPsbR2, and OsPsbP), and CO2 fixation. The metabolomic analysis identified 91 and 57 metabolite alterations induced by BR, primarily linked to amino acid, flavonoid, and lipid metabolism, with notable increases in antioxidant metabolites such as lignanoside, isorhamnetin, and L-glutamic acid. The integrated analysis highlighted the pivotal roles of 12-OPDA in α-linolenic acid metabolism and genes related to lipid metabolism, JA metabolism, and JA signal transduction in BR-mediated salt tolerance.

The evolutionary trajectories and gene regulatory roles of nuclear-integrated plastid DNA: clues for enhancing environmental adaptation in Caryophyllales

Environmental stimuli can induce the transfer of chloroplast DNA to the nuclear genome, resulting in nuclear-integrated plastid DNAs (NUPTs). However, their role in plant adaptability remains unclear. Species within the Caryophyllales order, known for their adaptation to extreme environments, provide an ideal model for studying the evolutionary dynamics and functions of NUPTs. In this study, we analyzed NUPTs in 24 Caryophyllales species to investigate their evolution and regulatory roles in gene expression, particularly in response to environmental stimuli. We found significant interspecies variation in NUPT abundance, ranging from 566 insertions in Amaranthus cruentus to 3585 in Beta vulgaris, with sizes spanning from 100 bp to over 100 kb. Approximately 62% of NUPTs were inserted within the last 20 million years, while some species exhibit insertion peaks dating back 49 million years. NUPT presence/absence polymorphisms in six related species suggest that NUPT insertions and deletions are dynamic processes influenced by phylogeny. NUPTs predominantly integrate into intergenic regions but also insert into genes and promoters, with certain regions acting as hotspots. Notably, NUPTs introduce numerous environmental-responsive cis-acting elements in promoter regions. Genes with NUPT insertions in their promoters are significantly enriched for functions related to environmental response. Further luciferase assays in Spinacia oleracea demonstrated that NUPT insertions can regulate the expression of genes related to environmental responses, indicating their potential role in adaptive evolution. Overall, our study provides insights into NUPT evolution and their influence on gene function and plant adaptability to environmental stimuli.

Squalene acts as a feedback signaling molecule in facilitating bidirectional communication between tea plants

Plants respond to environmental stimuli by releasing volatile organic compounds (VOCs), which play diverse roles in plant-to-plant interactions. Previous studies have primarily focused on how receiving plants respond. However, little is known about how these receivers communicate back to the emitter plants and their subsequent impacts. Our findings indicated increased plant tolerance when neighboring plants were present, suggesting bidirectional plant communication. Furthermore, we established a model to explore the role of signals from receiver plants, identifying squalene as a crucial feedback signal enhancing the cold tolerance in emitter plants by up-regulating CsCBF5 expression. Further analysis using yeast one-hybrid analysis coupled with inhibition of brassinosteroid pathways suggested that squalene-induced castasterone (CS) accumulation directly activated CsCBF5 expression modulated by CsBES1/BZR1. Overall, these results demonstrated the role of the squalene-CS-BES1/BZR1-CBF5 pathway in the bidirectional communication between plants, expanding our understanding of plant interactions.

Recent Advances in the Crosstalk between Brassinosteroids and Environmental Stimuli

Due to their sessile lifestyle, plants need to optimize their growth in order to adapt to ever-changing environments. Plants receive stimuli from the environment and convert them into cellular responses. Brassinosteroids (BRs), as growth-promoting steroid hormones, play a significant role in the tradeoff between growth and environmental responses. Here, we provide a comprehensive summary for understanding the crosstalk between BR and various environmental stresses, including water availability, temperature fluctuations, salinization, nutrient deficiencies and diseases. We also highlight the bottlenecks that need to be addressed in future studies. Ultimately, we suppose to improve plant environmental adaptability and crop yield by excavating natural BR mutants or modifying BR signaling and its targets.

Inter-subspecies diversity of maize to drought stress with physio-biochemical, enzymatic and molecular responses

Background

Drought is the most significant factor limiting maize production, given that maize is a crop with a high water demand. Therefore, studies investigating the mechanisms underlying the drought tolerance of maize are of great importance. There are no studies comparing drought tolerance among economically important subspecies of maize. This study aimed to reveal the differences between the physio-biochemical, enzymatic, and molecular mechanisms of drought tolerance in dent (Zea mays indentata), popcorn (Zea mays everta), and sugar (Zea mays saccharata) maize under control (no-stress), moderate, and severe drought stress.

Methods

Three distinct irrigation regimes were employed to assess the impact of varying levels of drought stress on maize plants at the V14 growth stage. These included normal irrigation (80% field capacity), moderate drought (50% field capacity), and severe drought (30% field capacity). All plants were grown under controlled conditions. The following parameters were analyzed: leaf relative water content (RWC), loss of turgidity (LOT), proline (PRO) and soluble protein (SPR) contents, membrane durability index (MDI), malondialdehyde (MDA), and hydrogen peroxide (H2O2) content, the antioxidant enzyme activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), and catalase (CAT). Additionally, the expression of heat shock proteins (HSPs) was examined at the transcriptional and translational levels.

Results

The effects of severe drought were more pronounced in sugar maize, which had a relatively high loss of RWC and turgor, membrane damage, enzyme activities, and HSP90 gene expression. Dent maize, which is capable of maintaining its RWC and turgor in both moderate and severe droughts, and employs its defense mechanism effectively by maintaining antioxidant enzyme activities at a certain level despite less MDA and H2O2 accumulation, exhibited relatively high drought tolerance. Despite the high levels of MDA and H2O2 in popcorn maize, the up-regulation of antioxidant enzyme activities and HSP70 gene and protein expression indicated that the drought coping mechanism is activated. In particular, the positive correlation of HSP70 with PRO and HSP90 with enzyme activities is a significant result for studies examining the relationships between HSPs and other stress response systems. The discrepancies between the transcriptional and translational findings provide an opportunity for more comprehensive investigations into the role of HSPs in stress conditions.

Exploring the effects of three-finger toxins from Naja ashei venom on neuronal and immunological cancer cell membranes

Three-finger proteins are the most abundant toxins in the venom of Naja ashei, a snake species from the Elapidae family. This research aimed to describe the effects of varying charges of these proteins, isolated from Naja ashei venom using SEC and IEX chromatography. The study examined how differently charged three-finger toxin fractions interact with and affect neuroblastoma (SK-N-SH) and promyeloblast (HL-60) cells, as well as model Langmuir membranes and liposomes designed to mimic cellular lipid composition. Findings revealed that protein surface charges significantly impact cell survival (MTT assay), membrane damage (lactate dehydrogenase release, malondialdehyde formation), and the structural and electrochemical properties of model membranes (Langmuir membranes and zeta potential for liposomes and cancer cell lines). Results indicated that SK-N-SH cells, characterized by a higher negative charge on their cell membranes, interacted more effectively with positively charged toxins than HL-60 cells. However, the mechanism of these electrostatic interactions is complex. The research demonstrated that electrostatic and mechanical membrane modifications induced by venom proteins can significantly affect cell metabolism. Additionally, the total charge of the membrane, influenced by polar lipid components and phospholipid saturation, plays a decisive role in toxin interaction.

Cold Acclimation and Deacclimation of Winter Oilseed Rape, with Special Attention Being Paid to the Role of Brassinosteroids

Winter plants acclimate to frost mainly during the autumn months, through the process of cold acclimation. Global climate change is causing changes in weather patterns such as the occurrence of warmer periods during late autumn or in winter. An increase in temperature after cold acclimation can decrease frost tolerance, which is particularly dangerous for winter crops. The aim of this study was to investigate the role of brassinosteroids (BRs) and BR analogues as protective agents against the negative results of deacclimation. Plants were cold-acclimated (3 weeks, 4 °C) and deacclimated (1 week, 16/9 °C d/n). Deacclimation generally reversed the cold-induced changes in the level of the putative brassinosteroid receptor protein (BRI1), the expression of BR-induced COR, and the expression of SERK1, which is involved in BR signal transduction. The deacclimation-induced decrease in frost tolerance in oilseed rape could to some extent be limited by applying steroid regulators. The deacclimation in plants could be detected using non-invasive measurements such as leaf reflectance, chlorophyll a fluorescence, and gas exchange monitoring.

Altered fatty acid composition confers improved drought acclimation in maize

Drought induces alteration in membrane lipid composition in plants; however, still little is known about whether membrane lipid remodeling plays a role in plant drought acclimation, including both drought tolerance and recovery, especially in crops. Here, we imposed natural progressive drought and re-watering in 18 maize genotypes at the seedling stage, and analyzed the physiological responses, drought tolerance and drought acclimation capabilities, contents of lipids, and fatty acid compositions. The results showed that drought caused significant reductions in shoot dry weight, relative water content, Fv/Fm, total lipid content, and double bond index (DBI) in most genotypes, while re-watering partially recovered these reductions. Meanwhile, the total lipid content, fatty acid composition, and DBI were also changed obviously in response to drought and re-watering. In order to explore the relationship between membrane lipid change and plant drought response, we did a principal component analysis. The results showed that C18:3 fatty acid contributed greatly to drought tolerance, and C16:2 and C16:3 fatty acids were more responsible for drought recovery. Meanwhile, DBI showed significant positive correlations with shoot dry weight and relative water content, but a negative association with lipid peroxidation, and more importantly, DBI was important for both drought tolerance and recovery. These alterations in membrane lipid composition may facilitate increasing membrane fluidity and decreasing membrane damage, thus maintaining the high photosynthetic capability under drought. Our results suggest that lipid remodeling is important for drought tolerance and recovery in crops, and different fatty acid species have different roles in crop drought acclimation.

New Paradigms in Brassinosteroids, Strigolactones, Sphingolipids, and Nitric Oxide Interaction in the Control of Lateral and Adventitious Root Formation

The root system is formed by the primary root (PR), which forms lateral roots (LRs) and, in some cases, adventitious roots (ARs), which in turn may produce their own LRs. The formation of ARs is also essential for vegetative propagation in planta and in vitro and for breeding programs. Root formation and branching is coordinated by a complex developmental network, which maximizes the plant's ability to cope with abiotic stress. Rooting is also a response caused in a cutting by wounding and disconnection from the donor plant. Brassinosteroids (BRs) are steroid molecules perceived at the cell surface. They act as plant-growth-regulators (PGRs) and modulate plant development to provide stress tolerance. BRs and auxins control the formation of LRs and ARs. The auxin/BR interaction involves other PGRs and compounds, such as nitric oxide (NO), strigolactones (SLs), and sphingolipids (SPLs). The roles of these interactions in root formation and plasticity are still to be discovered. SLs are carotenoid derived PGRs. SLs enhance/reduce LR/AR formation depending on species and culture conditions. These PGRs possibly crosstalk with BRs. SPLs form domains with sterols within cellular membranes. Both SLs and SPLs participate in plant development and stress responses. SPLs are determinant for auxin cell-trafficking, which is essential for the formation of LRs/ARs in planta and in in vitro systems. Although little is known about the transport, trafficking, and signaling of SPLs, they seem to interact with BRs and SLs in regulating root-system growth. Here, we review the literature on BRs as modulators of LR and AR formation, as well as their crosstalk with SLs and SPLs through NO signaling. Knowledge on the control of rooting by these non-classical PGRs can help in improving crop productivity and enhancing AR-response from cuttings.