Journal of Experimental Botany最新文献

This study combines electrophysiological, imaging, and molecular techniques to compare reactive oxygen species (ROS)-mediated K⁺/Na⁺ regulation in root elongation (EZ) and mature zones (MZ) of halophytic quinoa (Chenopodium quinoa) and glycophytic spinach (Spinacia oleracea). Under salinity stress, quinoa exhibited transient ROS (H2O2) accumulation followed by rapid recovery, whereas spinach showed prolonged oxidative stress and severe ionic imbalance in roots. Quinoa plants avoided cytosolic Na+ toxicity by excluding Na⁺ via the upregulation of salt overly sensitive (SOS1) genes and enhanced vacuolar sequestration via NHX. Quinoa maintained K⁺ homeostasis under ROS through biphasic regulation linked to tissue-specific expression of K+ transporter genes GORK, AKT1, HAK5, and KEA, while spinach possessed a sustained K⁺ loss. Transcriptomic analysis revealed quinoa's robust induction of MAPK signalling and ethylene-related genes, contrasting with spinach's reliance on ABA and delayed antioxidant responses. Overall, the differential sensitivity of root zones was attributed to quinoa's spatially restricted ROS signalling, which fine-tunes ion transporter activity, while spinach showed excessive ROS production and K+ loss. These results demonstrate that quinoa's oxidative tolerance arises from coordinated ROS-hormone-transporter interactions in a highly tissue-specific manner, providing a mechanistic framework for improving crop resilience.

Phytocystatins (plant cystatin) are a type of protease inhibitor widely studied for their specific and reversible inhibitory effects on cysteine proteases. The equilibrium between phytocystatins and their cysteine proteases plays key roles in biotic and abiotic stresses, plant immunity and so on. However, the roles of this balanced relationship in legume-rhizobium symbiosis remain poorly characterized. In the present study, we identified a nodule-specific cystatin gene GmCYS18 as a positive regulator of nodulation and nodule development in soybean. Over-expression of GmCYS18 increased Chlorophyll SPAD value, nodule number, plant height, weights of shoot, root and nodule, and the expression of nodulation marker genes, especially in the stable transgenic line GmCYS18-OX-1. Surprisingly, we found that GmCYS18 suppressed the expression of six root nodule symbiosis-related papain-like cysteine proteases (PLCP) in nodules. Furthermore, the GmPLCP gene, GmCYP17, which shows high homology to GmCYS9 that plays a negative regulatory role in soybean nodulation, was silenced by RNA interference (RNAi) system. The results showed that GmCYP17 inhibits nodulation, nodule development and the expression of nodulation marker genes in soybean. Our findings enriched the function of phytocystatins and provided insights into the correlation between cystatin and cysteine protease in nodule symbiosis.

DNA binding with one zinc finger (DOF) transcription factors (TFs) are specific to plants and have been shown to play diverse roles in plant-specific processes. However, their involvement in plant development is often obscured due to genetic redundancy. In this review, we focus on recent discoveries on the function of DOF TFs during plant development. We highlight the interplay between phytohormones, concretely auxin and cytokinin, and DOF TFs in the regulation of cambium proliferation, phloem development, and flower formation. We also discuss described roles of DOF TFs in plant regeneration. In the second part of the review, we examine reported interaction between DOF TFs and other proteins and transcriptional regulators. We emphasize the interactions between CYCLING DOF FACTORS (CDFs) and other proteins, which are necessary for a proper control of flowering time. Moreover, we highlight the interaction between the TFs CDF2 and PHYTOCHROME-INTERACTING FACTOR 4 (PIF4) as an example of how the joint activity of two different TFs can enhance the association to DNA and to the cooperative regulation of target genes. Lastly, we discuss challenges and future directions in the study of DOF TFs.

Activity of the root apical meristem and hence plant growth strictly depends on glutathione homeostasis. Despite compelling evidence for this dependency based on glutathione depletion, the cause for the growth arrest had remained unclear. Meristem control may depend on either the absolute amount of glutathione or on the glutathione redox potential (EGSH). To unambiguously distinguish those two options, we characterized an allelic series of six Arabidopsis mutants affected in glutamate-cysteine ligase, which catalyses the first step for the biosynthesis of reduced glutathione (GSH). When grown under the same conditions, even mutants with 20% and 50% of wild-type GSH amounts are slightly stunted. The most severely compromised mutants, zir1 and rml1, were crossed with either gr1, which lacks cyto-nuclear glutathione disulfide reductase and was used to induce a pronounced shift in EGSH, or with bir6, which has a diminished glutathione consumption and thus exhibits slightly increased levels of GSH. Based on theoretical considerations, these levels are not expected to shift the EGSH to any significant extent. Our study shows that deleting GR1 in the zir1 or rml1 background does not result in an obvious phenotypic change. By contrast, deleting BIR6 was sufficient to suppress the growth arrest in rml1 and to attenuate the growth restriction in zir1. These findings demonstrate that root growth is dependent on the availability of sufficient amounts of GSH, and not affected by pronounced changes in EGSH. This insight provides a decisive step towards understanding the mechanisms underpinning the proposed role of glutathione in growth control.

Leaf inclination, an essential characteristic of ideal plant architecture, plays a crucial role in determining crop yield by influencing leaf area index and planting density. Brassinosteroid (BR) serves as the major phytohormone involved in leaf inclination regulation, while the mechanism of BR signaling regulation in rice still needs exploration when compared to Arabidopsis. Here, a bHLH transcription factor OsbHLH55 was highly expressed in the lamina joint, the osbhlh55 gene editing mutants exhibited large leaf inclination resulted from increased size of parenchyma cells on the adaxial side of the lamina joint, while OsbHLH55 overexpression lines showed small leaf inclination. In addition, the osbhlh55 mutants were hypersensitive to BR and the expression was inhibited by BR, suggesting that OsbHLH55 was negatively regulated by BR. Genetic experiments verify that OsbHLH55 can directly bind to the promoter of OsWRKY53 to repress its expression, which is involved in the BR signaling pathway. Moreover, OsbHLH55 can interact with and be phosphorylated by the OsMAPK6 in vitro. Collectively, our investigation revealed OsbHLH55 as a negative regulator of rice BR signaling to function in leaf inclination regulation, and shedding light on the intricate interplay between BR and MAPK signaling pathways in rice.

Circadian rhythms, driven by an endogenous biological clock, align physiological processes with the Earth's 24-hour light-dark cycle, enabling organisms to adapt to diurnal environmental changes. In plants, the circadian clock regulates key physiological and metabolic processes, such as photosynthesis, nutrient uptake, and stress responses, thereby optimizing growth and development. Recent studies reveal that lipid metabolism is significantly influenced by the circadian clock and diurnal rhythm, which modulate the expression of lipid metabolic genes and ensures rhythmic production and degradation of lipids in response to energy availability and environmental conditions. This review highlights the circadian and diurnal regulation of fatty acid biosynthesis and membrane (phospho/galactolipids), storage (triacylglycerols), and surface (waxes) lipid metabolism in plants, while addressing the broader implications for plant adaptation to environmental changes and extreme stress conditions.

Accumulating scientific insights reveal the ecological and evolutionary implications of phenotypic plant plasticity in response to biotic and abiotic stress factors. This study confirms that root-knot nematode infection leads to intergenerational acquired resistance (IAR) in rice offspring. Genome-wide and targeted gene expression analyses demonstrated that offspring of nematode-infected rice plants are better prepared to fight against such attack through 'spring loading' of hormone-related plant defense genes. These genes are suppressed under basal conditions in IAR plants but show a more dramatic induction upon nematode attack. Here, ChIP-sequencing was executed on the offspring of IAR versus naive plants to investigate if histone modifications could be involved in the spring-loaded expression pattern. This revealed enrichment of H3K4me3 on defence related genes and H3K27me3 on development-related genes in roots of IAR plants. Detailed bio-informatic analyses pointed towards significant epigenetic changes to the ABA, ET and MAPK signalling pathways in the offspring of nematode-infected plants. A rice line with reduced activity for OsMPK5 was found to be deficient in defense spring loading and the IAR phenotype. Transmitting a memory of encountered stress factors to one's offspring is arguably an important asset for the adaptation of sessile plant communities to hostile environments.

Sorghum grains are rich in protein and starch but exhibit low protein digestibility, limiting their value for food and feed. However, the molecular mechanisms underlying these traits remain largely unknown, particularly the roles of structural genes and transcription factors (TFs) hindering efforts to improve grain quality. To address this, we constructed a gene co-expression network using transcriptome data from grain development in two different field seasons. In parallel, we quantified starch and protein content and measured protein digestibility. Two major gene co-expression modules were identified. The first was linked to the loss of protein digestibility, involving genes related to disulfide bonds formation and modulation. The second contained most kafirin and starch metabolism genes, as well as orthologs of TFs known to regulate protein and starch accumulation in other species. Functional assays in protoplasts for six TFs suggest a central role for SbPBF1a, SbPBF1b and SbNF-YC13 in modulating the expression of genes involved in protein and starch biosynthesis. This study provides new insights into the transcriptional regulation of protein and starch accumulation in sorghum. It identifies candidate regulatory and structural genes that offer promising targets for future validation and for improving grain quality in breeding programs.

Nitric oxide (NO) is a plant gasotransmitter that regulates plant growth and development by interacting with different regulatory pathways. Among these, brassinosteroids (BRs) have become candidate phytohormones that interact antagonistically and closely with NO to regulate plant growth. Seedling growth in NO-deficient mutants is enhanced and hyper-responds to BR treatments, while NO over-accumulator mutants show some developmental defects. Interestingly, this hyper-response was also observed in mutants that had both constitutively activated BRs signalling and reduced NO levels. BR signalling mutants exhibited different responses to the NO repressive role in seedlings. The phenotypes observed were attributed to the induction of BR-repressed biosynthetic genes and the repression of BR-induced growth-promoting genes detected in NO over-accumulating plants, with opposite gene expression patterns detected in NO-deficient plants. Furthermore, the activation of BR signalling has an impact on NO accumulation, as BR-treated plants or mutants with activated BR signalling showed hyper-accumulation of NO. Finally, elevated endogenous levels of brassinolide, the most bioactive BR, were found in NO-deficient plants, which could explain the growth promotion observed in this mutant. These findings contribute to a better understanding of the growth-repressive role of NO during seedling development through its interaction with BR biosynthesis, signalling, and responses.

Circadian clocks have long been hypothesized to tightly link cellular and physiological processes to the appropriate time within the twenty-four-hour cycle of the earth's daily rotation. According to this hypothesis, circadian rhythms with cycle lengths that differ significantly from twenty-four hours would be disadvantageous, as they would generate a desynchronization between the endogenous and exogenous cycles that would place stress upon an organism through the required daily resetting at dawn. However, recent work has demonstrated that endogenous circadian cycles that differ from twenty-four hours by two hours or more are prevalent within the green lineage. Herein, we review recent work on the prevalence of and adaptive advantages associated with natural variation in circadian cycles. Based on known photoperiodic sensing mechanisms we also describe a set of principles that allow the same changes in circadian period to cause different plant responses. This fine-tuning of clock output pathways provides a flexible mechanism enabling plants to use a wide range of life history strategies for plant adaptation to different environmental niches. Further studies are needed to determine how variations of the clock and other signals are integrated in different plants. These studies highlight the circadian clocks' position as a prime adaptation target for migration of plant species into new environmental ranges.