Journal of Experimental Botany最新文献

Cytosine (DNA) methylation plays important roles in silencing transposable elements, plant development, genomic imprinting, stress responses, and maintenance of genome stability. To better understand the functions of this epigenetic modification, several tools have been developed to manipulate DNA methylation levels. These include mutants of DNA methylation writers and readers, targeted manipulation of locus-specific methylation, and the use of chemical inhibitors. Here, we summarize the effects of commonly used cytidine analog chemical inhibitors represented by zebularine, 5-azacytidine, and their related compounds on plants. These analogs are incorporated into the chromosomal DNA, where they block the activity of the replicative CG DNA methyltransferase 1 (MET1). This leads to manifold alterations in plant epigenome, modified developmental programs, or suppression of hybridization barriers. We also highlight the DNA-damaging effects of cytidine analogs, particularly the formation of stable DNA-protein crosslinks between DNA and MET1. This sheds new light on specific phenotypes observed upon cytidine analog treatments. In conclusion, cytidine analogs remain a vital tool for plant genome research and have the potential to open new promising avenues for applications in plant biotechnology and breeding.

During their lifespan, plants are often exposed to a broad range of stresses that change their redox balance and lead to accumulation of reactive oxygen species (ROS). The traditional view is that this comes with negative consequences to cells structural integrity and metabolism and, to prevent this, plants evolved a complex and well-coordinated antioxidant defence system that relies on the operation of a range of enzymatic and non-enzymatic antioxidants (AO). Due to the simplicity of measuring their activity, and in the light of the persistent dogma that stress-induced ROS accumulation is detrimental for plants, it is not surprising that enzymatic AO have often been advocated as suitable proxies for stress tolerance, as well as potential targets for improving tolerance traits. However, there is a growing number of reports showing either no changes or even downregulation of AO systems in stressed plants. Moreover, ROS are recognised now as important second messengers operating in both local and systemic signalling, synergistically interacting with the primary stressor, to regulate gene expression needed for optimal acclimatization. This work critically assesses the suitability of using enzymatic AO as a proxy for stress tolerance, or as a target for crop genetic improvement. It is concluded that constitutively higher AO activity may interfere with stress-induced ROS signalling and be of disadvantage to plant stress tolerance.

In aerobic life forms, reactive oxygen species (ROS) are produced by the partial reduction of oxygen during energy-generating metabolic processes. In plants, ROS production increases during periods of both abiotic and biotic stress, severely overloading the antioxidant systems. Hydrogen peroxide (H2O2) plays a central role in cellular redox homeostasis and signaling by oxidising crucial cysteines to sulfenic acid, which is considered a biologically relevant post-translational modification (PTM). Until now, the impact of the nucleus on cellular redox homeostasis has been relatively unexplored. The regulation of histone-modifying enzymes by oxidative PTMs at redox-sensitive cysteine or tyrosine residues is particularly intriguing because it allows the integration of redox signaling mechanisms with chromatin control of transcriptional activity. One of the most extensively studied histone acetyltransferases is the conserved GENERAL CONTROL NONDEPRESSIBLE 5 (GCN5) complex. This study investigated the nuclear sulfenome in Arabidopsis thaliana by expressing a nuclear variant of the Yeast Activation Protein-1 (YAP1) probe and identified 225 potential redox-active proteins undergoing S-sulfenylation. Mass spectrometry analysis further confirmed the S-sulfenylation of GCN5 at cysteines 293, 368, and 400, and their functional significance and impact on the GCN5 protein-protein interaction network were assessed using cysteine-to-serine mutagenesis.

Our current agricultural system faces a perfect storm-climate change, burgeoning population, and unpredictable outbreaks like COVID-19 disrupt food production, particularly for vulnerable populations in developing countries. A paradigm shift in agriculture practices is needed to tackle these issues. One solution is the diversification of crop production. While ~56% of the protein consumed from plants stems from three major cereal crops (rice, wheat and maize), underutilized crops such as millets, legumes and other cereals are highly neglected by farmers and the research community. Millets are one of the most ancient and versatile orphan crops with attributes like fast-growing, high-yielding, withstanding harsh environments, and rich in micronutrients such as iron and zinc, making them appealing to achieve agronomic sustainability. Here, we highlight the contribution of millet to agriculture and pay attention to the latest research on the genetic diversity of millet, genomic resources, and next-generation omics and their applications under various stress conditions. Additionally, integrative omics technologies could identify and develop millets with desirable phenotypes having high agronomic value and mitigating climate change. Here, we emphasize that biotechnological interventions, such as genome-wide association, genomic selection, genome editing, and artificial intelligence/machine learning, can improve and breed millets more effectively.

Assembling and remodelling the cell wall is essential for plant development. Cell wall dynamics is controlled by cell wall proteins, polysaccharide biosynthesis, and a variety of sensor and receptor systems. LecRK-I.9, an Arabidopsis thaliana plasma membrane-localised lectin receptor kinase, was previously shown to be involved in cell wall-plasma membrane contacts and to play roles in plant-pathogen interactions, but so far, its role in development was unknown. LecRK-I.9 is transcribed at a high level in root tissues including the pericycle. Comparative transcript profiling of a loss-of-function mutant vs wild type identifies LecRK-I.9 as a regulator of cell wall metabolism. Consistently, lecrk-I.9 mutants display an increased pectin methylesterification level correlated with decreased pectin methylesterase and increased polygalacturonase activities. Also, LecRK-I.9 negatively impacts lateral root development through the direct or indirect regulation of genes encoding (i) cell wall remodelling proteins during early events of lateral root initiation, and (ii) cell wall signalling peptides (CLE2, CLE4) repressing lateral root emergence and growth. Besides, low nitrate reduces LecRK-I.9 expression in roots, particularly in the lateral root emergence zone: even in these conditions, the control of CLE2 and CLE4 expression is maintained. Altogether, the results show that LecRK-I.9 is a key player in negatively regulating both pre-branch site formation and lateral root emergence.

Phosphorus (P) is an essential macronutrient for the growth and yield of crops. However, there is limited understanding of the regulatory mechanisms of phosphate (Pi) homeostasis, and its impact on growth, development, and yield-related traits in Brassica napus. Here, we identified four NITROGEN LIMITATION ADAPATATION1 (BnaNLA1) genes in B. napus, their expression was predominant in roots and suppressed by Pi starvation-induced MicroRNA827s (BnamiR827s). All the BnaNLA1 proteins have similar sequences, subcellular localizations, and abilities to rescue the growth defects of atnla1 mutant. One of the genes, BnaA09.NLA1 expressed abundantly in roots, and also in old leaves, anthers and pollens. Knocking out of BnaNLA1(s) or overexpressing BnamiR827 resulted in increased concentrations of Pi in leaves as well as in stamen and had reduced pollen viability thereby negatively impacting seed yield. BiFC and split-ubiquitin Y2H analyses demonstrated that BnaA09.NLA1 interacted with seven Pi transporters highly expressed in roots and/or anthers (i.e., BnaPT8/10/11/27/35/37/42) to regulate Pi uptake and Pi allocation in anthers. Taken together, this study demonstrates that the BnamiR827-BnaA09.NLA1-BnaPHT1s module is involved in regulating Pi uptake and Pi allocation in floral organs, which is vital for the growth, pollen viability and seed yield of B. napus.

Bidirectional communication between pathogenic microbes and their plant hosts via small (s)RNA-mediated cross-kingdom RNA interference (ckRNAi) is a key element for successful host colonisation. Whether mutualistic fungi of the Serendipitaceae family, known for their extremely broad host range, use sRNAs to colonize plant roots is still under debate. To address this question, we developed a pipeline to validate the accumulation, translocation, and activity of fungal sRNAs in post-transcriptional silencing of Arabidopsis thaliana genes. Using stem-loop RT-qPCR, we detected the expression of a specific set of Serendipita indica (Si)sRNAs, targeting host genes involved in cell wall organization, hormonal signalling regulation, immunity, and gene regulation. To confirm the gene silencing activity of these sRNAs in plant cells, SisRNAs were transiently expressed in protoplasts. Stem-loop PCR confirmed sRNAs expression and accumulation, while qPCR validated post-transcriptional gene silencing of their predicted target genes. Furthermore, Arabidopsis ARGONAUTE 1 immunoprecipitation (AtAGO1-IP) revealed the loading of fungal SisRNAs into the plant RNAi machinery, suggesting the translocation of SisRNA from the fungus into root cells. In conclusion, this study provides a blueprint for rapid selection and analysis of sRNA effectors and further supports the model of cross-kingdom communication in the Sebacinoid symbiosis.

Null mutations for genes encoding a major seed storage protein in pea, vicilin, were sought through screening a fast-neutron mutant population. Deletion mutations at four or five vicilin loci, where all vicilin genes within each locus were deleted, were combined to address the question of how removal or reduction of a major storage protein and potential allergen might impact the final concentration of protein per unit mature seed weight, seed yield and viability. While the concentration of seed protein was not reduced in mature seeds of mutant lines, indicative of a re-balancing of the proteome, notable differences were apparent in the metabolite, proteomic and amino acid profiles of the seeds, as well as in some functional properties. Major effects of the deletions on the proteome were documented. The genomic regions which were deleted were defined by whole genome sequencing of the parental line, JI2822 and its quintuple vicilin null derivative, providing a comprehensive description of each vicilin locus and its genic arrangement. An annotated reference genome has been generated for JI2822, which will serve as a very valuable resource for the research community and support further study of the associated deletion mutant population.

While evolutionary studies indicate that the most ancient groups of organisms on Earth likely descended from a common wall-less ancestor, contemporary organisms lacking a carbohydrate-rich cell surface are exceedingly rare. By developing a cell wall to cover the plasma membrane, cells were able to withstand higher osmotic pressures, colonise new habitats and develop complex multicellular structures. This way, the cells of plants, algae and microorganisms are covered by a cell wall, which can generally be defined as a highly complex structure whose main framework is usually composed of carbohydrates. Rather than static structures, they are highly dynamic and serve a multitude of functions that modulate vital cellular processes, such as growth and interactions with neighbouring cells or the surrounding environment. Thus, despite its vital importance for many groups of life, it is striking that there are few comprehensive documents comparing the cell wall composition of these groups. Thus, the aim of this review was to compare the cell walls of plants with those of algae and microorganisms, paying particular attention to their polysaccharide components. It should be highlighted that, despite the important differences in composition, we have also found numerous common aspects and functionalities.