Journal of Experimental Botany最新文献

Several plant seeds release a mucilaginous envelope through hydration, rich in pectins and stabilized by cellulose fibers. This mucilage aids in seed protection, development, and adhesion for dispersal. This study aimed to separate the effects of pectins and cellulose fibers by using pectinase to remove mucilage pectins, leaving cellulose arrays, and performing wet and dry pull-off force measurements on seeds of three plant species: Salvia hispanica (Chia), Collomia grandiflora (Collomia) and Linum usitatissimum (Flax). We used light and scanning electron microscopy to confirm partial pectin removal and intact cellulose fibers. Pull-off force measurements revealed similar wet adhesive properties and E-moduli in S. hispanica and C. grandiflora seeds before and after pectin removal. L. usitatissimum seeds, lacking cellulose fibers, exhibited significantly lower wet and dry adhesion forces post-pectin removal. Desiccation dynamics showed shorter desiccation times after pectin removal in all three species. Results indicated that adhesion forces in seed mucilage with cellulose fibers did not change significantly after pectin removal, suggesting that cellulose fibers contribute to the adhesive properties of seed mucilage, while pectins might not play an exclusive role in adhering to surfaces.

The Arabidopsis root apical meristem is an excellent model for studying plant organ growth that involves a coordinated process of cell division, elongation, and differentiation, while each tissue type develops on its own schedule. Among these tissues, the protophloem is particularly important, differentiating early to supply nutrients and signalling molecules to the growing root tip. The OCTOPUS (OPS) protein and its homolog OPS-LIKE 2 (OPL2) are essential for proper root protophloem differentiation and, likely through this role, indirectly promote root growth. Here, we explored the roles of the other three OPS homologs in Arabidopsis, OPL1, OPL3, and OPL4. OPS/OPL genes exhibit overlapping expression patterns and functions, with a high degree of redundancy among them. Although higher-order mutants do not display more severe phloem defects, they exhibit significantly reduced root growth compared to the ops opl2 mutant. These results suggest a direct contribution of the investigated OPL genes to meristematic activity. While our focus was on root growth, the OPS/OPL gene family also plays a positive role in regulating shoot growth, emphasizing its broader impact on plant development. Furthermore, our analyses reiterate the central role of OPS and the phloem domain in controlling overall plant growth.

A well-constructed pollen wall is essential for pollen fertility, which relies on the contribution of tapetum. Our results demonstrate an essential role of the tapetum-expressed protein phosphatase 2A (PP2A) B'α and B'β in pollen wall formation. The b'aβ double mutant pollen grains harbored sticky remnants and tectum breakages, resulting in failed release. B'α and B'β function partially through dephosphorylating and activating BZR1. The bzr1 bes1 double and higher-order mutants of this family displayed similar defects in pollen wall, while bzr1-1D, having an active mBZR1 exhibited fertile pollen grains in a B'α and B'β dependent manner. Correspondingly, the level of phospho-BZR1 is increased and dephospho-BZR1 is decreased in b'aβ and bzr1-1D/b'aβ at anther stages 8-9 as compared with Col-0 and bzr1-1D, respectively. A cysteine protease gene CEP1 was identified as a BZR1 target, whose transcriptional activation necessitates BRREs in the promoter region and BZR1 DNA binding domain. The mRNA level of CEP1 at stages 8-9 was extremely low in bzr1 and bzr1 bes1, while higher in Col-0 and bzr1-1D depending on B'α and B'β. Furthermore, cep1 mutants displayed similar defects in pollen wall. In brief, this study uncovered a PP2A-BZR1-CEP1 regulatory module, providing a new insight into pollen maturation mechanism.

Plastid-localized plastoglobules (PGs) are monolayer lipid droplets typically associated with the outer envelope of thylakoid membranes in chloroplasts. The size and number of PGs can vary significantly in response to different environmental stimuli. Since the early 21st century, a variety of proteins attached to the surface of PGs have been identified and experimentally characterized using advanced biotechnological techniques, revealing their biological functions. This article aims to review the latest discoveries regarding PG-associated proteins and explore their dynamics under both single and combined abiotic stress conditions, providing insights into the critical role of plastid lipid droplets in plant adaptation to global climate-related challenges.

Through extensive research, nitroxyl (HNO) has emerged as a newly recognized redox signal in plant developmental and stress responses. The interplay between nitric oxide (●NO) and HNO entails a complex network of signaling molecules and regulatory elements sensitive to the environment's specific redox conditions. However, functional implications for HNO in cell signaling require more detailed studies, starting with identifying HNO-level switches. To obtain insight into possible physiologically relevant HNO modulators, we examined via real-time detection the HNO/●NO production triggered by selected plant-related compounds (PRCs), including non-protein amino acids, antioxidants, and phytohormones both in vitro and in vivo in the model plant Arabidopsis thaliana. Hydrogen sulfide, ascorbic acid, and salicylic acid were identified as superior PRCs in driving HNO/●NO interconversion in the cellular medium so that these PRCs could provide ubiquitous bioavailability of HNO in plants. Meanwhile, resistance-inducing compounds tended to downregulate HNO in Arabidopsis leaves. The present study indicates that non-enzymatic HNO/●NO interconversion mediated by functionally important PRCs constitutes a significant route for controlling endogenous HNO levels, providing ubiquitous HNO bioavailability in plant cells. Moreover, concurrent HNO/●NO monitoring shows that the redox signals are highly integrated and create a redox code that can be translated into a specific cell response.

Sorghum is emerging as an ideal genetic model for designing high-biomass bioenergy crops. Biomass yield, a complex trait influenced by various plant architectural characteristics, is typically regulated by numerous genes. This study aimed to dissect the genetic regulators underlying fourteen plant architectural traits and ten biomass yield traits in the Sorghum Association Panel across two growing seasons. We identified 321 associated loci through genome-wide association studies (GWAS), involving 234,264 single nucleotide polymorphisms (SNPs). These loci include genes with known associations to biomass traits, such as 'maturity', 'dwarfing (Dw)', and 'leafbladeless1', as well as several uncharacterized loci not previously linked to these traits. We also identified 22 pleiotropic loci associated with variation in multiple phenotypes. Three of these loci, located on chromosomes 3 (S03_15463061), 6 (S06_42790178; Dw2), and 9 (S09_57005346; Dw1), exerted significant and consistent effects on multiple traits across both growing seasons. Additionally, we identified three genomic hotspots on chromosomes 6, 7, and 9, each containing multiple SNPs associated with variation in plant architecture and biomass yield traits. Chromosome-wise correlation analyses revealed multiple blocks of positively associated SNPs located near or within the same genomic regions. Finally, genome-wide correlation-based network analysis showed that loci associated with flowering, plant heights, leaf traits, plant density, and tiller number per plant were highly interconnected with other genetic loci influencing with plant architectural and biomass yield traits. The pyramiding of favorable alleles related to these traits holds promise for enhancing the future development of bioenergy sorghum crops.

Adenine metabolism is important for common bean (Phaseolus vulgaris L.) productivity since this legume uses ureides derived from the oxidation of purine nucleotides as its primary nitrogen storage molecules. Purine nucleotides are produced from de novo synthesis or through salvage pathways. Adenine phosphoribosyl transferase (APRT) is the enzyme dedicated to adenine nucleobase salvage for nucleotide synthesis, but it can also convert active cytokinin bases into their inactive nucleotide forms. In common bean, APRT is encoded by four genes. Gene expression analysis, biochemical properties, and subcellular location indicated functional differences among the common bean APRT isoforms. CRISPR/Cas9 targeted down-regulation of two of the four PvAPRTs followed by metabolomic and physiological analyses of targeted hairy roots revealed that, although the two proteins have redundant functions, PvAPRT1 mostly participated in the salvage of adenine, whereas PvAPRT5 was the predominant form in the regulation of cytokinin homeostasis and stress responses with a high impact in root and nodule growth.

Archaeplastida, a group of photosynthetic organisms with primary plastids, consists of green algae (plus land plants), red algae, and glaucophytes. In contrast to green and red algae, information on lipids and lipid biosynthesis is still incomplete in the glaucophytes. The chloroplast is the site of photosynthesis and fatty acid synthesis in all photosynthetic organisms known to date. However, the genomic data of the glaucophyte Cyanophora paradoxa indicated the lack of acetyl-CoA carboxylase and most components of fatty acid synthase in the chloroplast. Instead, multifunctional fatty acid synthase and acetyl-CoA carboxylase are likely to reside in the cytosol. To examine this hypothesis, we measured fatty acid synthesis in isolated chloroplasts and whole cells using stable isotope labeling. The chloroplasts had very low fatty acid synthesis activity, if any. Most processes of fatty acid synthesis, including elongation and desaturation, must be performed within the cytosol, and the fatty acids imported into the chloroplasts are assembled into the chloroplast lipids by the enzymes common to other algae and plants. Cyanophora paradoxa is a rare organism in which fatty acid synthesis and photosynthesis are not tightly linked. This could question the common origin of these two biosynthetic processes in Archaeplastida.

Evaluation of relevant seed traits is an essential part of most plant breeding and biotechnology programmes. There is a need for non-destructive, three-dimensional assessment of the morphometry, composition, and internal features of seeds. Here, we introduce a novel tool, MRI-Seed-Wizard, which integrates deep learning algorithms with non-invasive magnetic resonance imaging (MRI) for use in a new domain-plant MRI. The tool enabled in vivo quantification of 23 grain traits, including volumetric parameters of inner seed structure. Several of these features cannot be assessed using conventional techniques, including X-ray computed tomography. MRI-Seed-Wizard was designed to automate the manual processes of identifying, labeling, and analysing digital MRI data. We further provide advanced MRI protocols that allow the evaluation of multiple seeds simultaneously to increase throughput. The versatility of MRI-Seed-Wizard in seed phenotyping is demonstrated for wheat (Triticum aestivum) and barley (Hordeum vulgare) grains, and it is applicable to a wide range of crop seeds. Thus, artificial intelligence, combined with the most versatile imaging modality, MRI, opens up new perspectives in seed phenotyping and crop improvement.