Phospholipase A enzymes cleave phospho- and galactolipids to generate free fatty acids and lysolipids that function in animal and plant hormone signaling. Here, we describe three Arabidopsis patatin-related phospholipase A (pPLA) genes AtPLAIVA, AtPLAIVB, and AtPLAIVC and their corresponding proteins. Loss-of-function mutants reveal roles for these pPLAs in roots during normal development and under phosphate deprivation. AtPLAIVA is expressed strongly and exclusively in roots and AtplaIVA-null mutants have reduced lateral root development, characteristic of an impaired auxin response. By contrast, AtPLAIVB is expressed weakly in roots, cotyledons, and leaves but is transcriptionally induced by auxin, although AtplaIVB mutants develop normally. AtPLAIVC is expressed in the floral gynaecium and is induced by abscisic acid (ABA) or phosphate deficiency in roots. While an AtplaIVC-1 loss-of-function mutant displays ABA responsiveness, it exhibits an impaired response to phosphate deficiency during root development. Recombinant AtPLA proteins hydrolyze preferentially galactolipids and, less efficiently, phospholipids, although these enzymes are not localized in chloroplasts. We find that AtPLAIVA and AtPLAIVB are phosphorylated by calcium-dependent protein kinases in vitro and this enhances their activities on phosphatidylcholine but not on phosphatidylglycerol. Taken together, the data reveal novel functions of pPLAs in root development with individual roles at the interface between phosphate deficiency and auxin signaling.
Drought is a major cause of losses in crop yield. Under field conditions, plants exposed to drought are usually also experiencing rapid changes in light intensity. Accordingly, plants need to acclimate to both, drought and light stress. Two crucial mechanisms in plant acclimation to changes in light conditions comprise thylakoid protein phosphorylation and dissipation of light energy as heat by non-photochemical quenching (NPQ). Here, we analyzed the acclimation efficacy of two different wheat varieties, by applying fluctuating light for analysis of plants, which had been subjected to a slowly developing drought stress as it usually occurs in the field. This novel approach allowed us to distinguish four drought phases, which are critical for grain yield, and to discover acclimatory responses which are independent of photodamage. In short-term, under fluctuating light, the slowdown of NPQ relaxation adjusts the photosynthetic activity to the reduced metabolic capacity. In long-term, the photosynthetic machinery acquires a drought-specific configuration by changing the PSII-LHCII phosphorylation pattern together with protein stoichiometry. Therefore, the fine-tuning of NPQ relaxation and PSII-LHCII phosphorylation pattern represent promising traits for future crop breeding strategies.
Cereal grain germination provides the basis for crop production and requires a tissue-specific interplay between the embryo and endosperm during heterotrophic germination involving signalling, protein secretion, and nutrient uptake until autotrophic growth is possible. High salt concentrations in soil are one of the most severe constraints limiting the germination of crop plants, affecting the metabolism and redox status within the tissues of germinating seed. However, little is known about the effect of salt on seed storage protein mobilization, the endomembrane system, and protein trafficking within and between these tissues. Here, we used mass spectrometry analyses to investigate the protein dynamics of the embryo and endosperm of barley (Hordeum vulgare, L.) at five different early points during germination (0, 12, 24, 48, and 72 h after imbibition) in germinated grains subjected to salt stress. The expression of proteins in the embryo as well as in the endosperm was temporally regulated. Seed storage proteins (SSPs), peptidases, and starch-digesting enzymes were affected by salt. Additionally, microscopic analyses revealed an altered assembly of actin bundles and morphology of protein storage vacuoles (PSVs) in the aleurone layer. Our results suggest that besides the salt-induced protein expression, intracellular trafficking and actin cytoskeleton assembly are responsible for germination delay under salt stress conditions.
cereal endosperm is a short-lived tissue adapted for nutrient storage, containing specialized organelles, such as protein bodies (pBs) and protein storage vacuoles (pSVs), for the accumulation of storage proteins. During development, protein trafficking and storage require an extensive reorganization of the endomembrane system. Consequently, endomembrane-modifying proteins will influence the final grain quality and yield. However, little is known about the molecular mechanism underlying endomembrane system remodeling during barley grain development. By using label-free quantitative proteomics profiling, we quantified 1,822 proteins across developing barley grains. Based on proteome annotation and a homology search, 94 proteins associated with the endomembrane system were identified that exhibited significant changes in abundance during grain development. Clustering analysis allowed characterization of three different development phases; notably, integration of proteomics data with in situ subcellular microscopic analyses showed a high abundance of cytoskeleton proteins associated with acidified PBs at the early development stages. Moreover, endosomal sorting complex required for transport (ESCRT)-related proteins and their transcripts are most abundant at early and mid-development. Specifically, multivesicular bodies (MVBs), and the ESCRT-III HvSNF7 proteins are associated with PBs during barley endosperm development. Together our data identified promising targets to be genetically engineered to modulate seed storage protein accumulation that have a growing role in health and nutritional issues. After differentiation, fully developed cereal endosperm makes up to 75% of the grain weight and covers four major cell types: aleurone, starchy endosperm, transfer cells, and the cells of the embryo surrounding region 1. The starchy endosperm thereby is characterized as a storage site, accumulating starch and seed storage proteins (SSPs) 2. The aleurone layer plays essential roles during seed germination and mobilizes starch and SSP reserves in the starchy endosperm by releasing hydrolytic enzymes that are responsible for the degradation of stored nutrients in the endosperm 2. Contrary to the persistent endosperm of cereals, the cellular endosperm of Arabidopsis thaliana (A. thaliana) supports the developing and growing embryo, resulting in a gradually depleted endosperm as the embryo grows. Finally, the massive A. thaliana embryo is only accompanied by a single peripheral layer, the aleurone layer, in mature seeds 2. Consequently, A. thaliana cannot to be used as a model system to study the endomembrane system in grain endosperm.
Background: Birch pollen-related apple allergy is the most frequent IgE-mediated food allergy in Central-Northern Europe with Mal d 1 as major allergen. Its concentration in apples varies with the cultivar and storage time. Year-round appealing, hypoallergenic cultivars still are needed to satisfy the nutritional needs of affected individuals. We characterized three promising cultivars by multidisciplinary in vitro assays including long-term storage and by clinical challenges of allergic individuals before and after the birch pollen season. Methods: Proteins were extracted from fruits of 'Santana', 'Golden Delicious' (GD), and three genuine cultivars in November 2018 and April 2019. Mal d 1-levels were analysed by mass spectrometry, SDS-PAGE, immunoblotting, competitive ELISA, and basophil activation tests. Twenty-eight allergic individuals underwent singleblinded open food challenges and skin testing with the cultivars and birch pollen in November 2018 and May 2019. Allergen-specific IgE-levels were determined. Results: After storage all cultivars except 'Santana' were of appealing appearance and taste. Their Mal d 1 content had increased, also reflected by significantly amplified basophil activation and stronger reactions in clinical challenges. Besides, individuals showed boosted reactivity after pollen exposure indicated by enhanced allergen-specific IgE-levels and skin reactions to birch pollen. Still, all cultivars remained significantly less allergenic than GD and comparable to Santana in November 2018 in all assessments except for skin testing.
Twitter: @VerenaIbl m: 4; f: 7 Abbreviations AMSH1, associated molecule with the SH3 domain of Stam1; A. AbstractCereal endosperm is a short-lived tissue adapted for nutrient storage, containing specialized organelles, such as protein bodies (PBs) and protein storage vacuoles (PSVs), for the accumulation of storage proteins. PBs can be used as efficient biotechnological systems to produce high yields of stable recombinant proteins. During development, protein trafficking and storage require an extensive reorganization of the endomembrane system. Consequently, endomembrane-modifying proteins will influence the final grain quality, yield and recombinant protein production. Barley, a cereal crop of worldwide importance for the brewing industry, animal feed and to a lesser extent, human nutrition, has been identified as promising candidate for recombinant protein production. However, little is known about the molecular mechanism underlying endomembrane system remodeling during barley grain development. By using in vivo label-free quantitative proteomics profiling, we quantified 1,822 proteins across developing barley grains. Based on proteome annotation and a homology search, 95 proteins associated with the endomembrane system were identified, and 83 of these exhibited significant changes in abundance during grain development. Clustering analysis allowed characterization of three different development stages; notably, integration of proteomics data with in situ subcellular microscopic analyses showed a high abundance of cytoskeleton proteins associated with acidified protein bodies at the early development stages. Endosomal sorting complex required for transport (ESCRT)-related proteins and their transcripts are most abundant at early and mid-development. Specifically, multivesicular bodies (MVBs), and the ESCRT-III HvSNF7 proteins are associated with protein bodies (PBs) during barley endosperm development. Taken together, our proteomics results specifically identified members of the cytoskeleton, MVBs, and ESCRT as putative key players for protein sorting into PBs during barley endosperm development. These results present a comprehensive overview of proteins involved in the rearrangement of the endomembrane system during barley early grain development and will provide the basis for future work on engineering the endomembrane system to optimize nutrient content and to produce high yields of recombinant proteins.
Roots are the hidden parts of plants, anchoring their above ground counterparts in the soil. They are responsible for water and nutrient uptake, as well as for interacting with biotic and abiotic factors in the soil. The root system architecture (RSA) and its plasticity are crucial for resource acquisition and consequently correlate with plant performance, while being highly dependent on the surrounding environment, such as soil properties and therefore environmental conditions. Thus, especially for crop plants and regarding agricultural challenges, it is essential to perform molecular and phenotypic analyses of the root system under conditions as near as possible to nature (#asnearaspossibletonature). To prevent root illumination during experimental procedures, which would heavily affect root development, dark-root (D-Root) devices (DRDs) have been developed. In this article, we describe the construction and different applications of a sustainable, affordable, flexible, and easy to assemble open-hardware bench-top LEGO DRD, the DRD-BIBLOX (Brick Black Box). The DRD-BIBLOX consists of one or more 3D-printed rhizoboxes which can be filled with soil, while still providing root visibility. The rhizoboxes sit in a scaffold of secondhand LEGObricks, which allows root development in the dark as well as non-invasive root-tracking with an infrared (IR) camera and an IR light emitting diode (LED) cluster. Proteomic analyses confirmed significant effects of root illumination on barley root and shoot proteome. Additionally, we confirmed the significant effect of root illumination on barley root and shoot phenotypes. Our data therefore reinforces the importance of the application of field conditions in the lab and the value of our novel device, the DRD-BIBLOX. We further provide a DRD-BIBLOX application spectrum, spanning from investigating a variety of plant species and soil conditions as well as simulating different environmental conditions and stresses, to proteomic and phenotypic analyses, including early root tracking in the dark.
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