Genetic and Hormonal Regulation of Chlorophyll Degradation during Maturation of Seeds with Green Embryos

The interplay of growth-regulating factor 5 and BZR1 in coregulating chlorophyll degradation in poplar

Chlorophyll (Chl) is essential for plants to carry out photosynthesis, growth and development processes. Growth-regulating factors (GRFs) play a vital role in regulating Chl degradation in plants. However, the molecular mechanism by which GRF5 regulates Chl degradation in poplar remains unknown. Here we found that overexpression of PpnGRF5-1 increased Chl content in leaves and promoted chloroplast development in poplar. Overexpression of PpnGRF5-1 in poplar delayed Chl degradation induced by external factors, such as hormones, darkness and salt stress. PpnGRF5-1 responded to brassinosteroid (BR) signalling during BR-induced Chl degradation and reduced the expression levels of Chl degradation and senescence-related genes. PpnGRF5-1 inhibited the expression of Chl b reductases PagNYC1 and PagNOL. PpnGRF5-1 could interact with PagBZR1 in the nucleus. PagBZR1 also inhibited the expression of PagNYC1. In addition, we found that the protein-protein interaction between PagBZR1 and PpnGRF5-1 enhanced the inhibitory effect of PpnGRF5-1 on the Chl b reductases PagNYC1 and PagNOL. BZR1 and GRF5-1 were upregulated, and NOL and NYC1 were downregulated in triploid poplars compared to diploids. This study revealed a new mechanism by which PpnGRF5-1 regulates Chl degradation in poplars and lays the foundation for comprehensively analysing the molecular mechanism of Chl metabolism in triploid poplars.

Heterologous expression of Zygophyllum xanthoxylon zinc finger protein gene (ZxZF) enhances the tolerance of poplar photosynthetic function to drought stress

The ZxZF transcription factor (TF) of Zygophyllum xanthoxylon (Bunge) Maxim, an extremely drought-resistant woody plant, is a C₂H₂ zinc finger protein. Studies have shown that C₂H₂ zinc finger proteins play important roles in activating stress-related genes and enhancing plant resistance. However, their function in regulating plant photosynthesis under drought stress is not well understood. Since poplar is an important greening and afforestation tree species, it is particularly important to cultivate excellent drought-tolerant varieties. The ZxZF transcription factor (TF) was heterogeneously expressed in Euroamerican poplar (Populus × euroameracana cl.'Bofengl') by genetic transformation. Based on the mechanism and potential function of poplar photosynthesis regulated by ZxZF under drought stress, transcriptomic and physiological determinations were used to reveal the important role of this gene in improving the drought resistance of poplar. The results showed that the overexpression of ZxZF TF in transgenic poplars could improve the inhibition of Calvin cycle by regulating stomatal opening and increasing the concentration of intercellular CO₂. The chlorophyll content, photosynthetic performance index, and photochemical efficiency of transgenic lines under drought stress were significantly higher than those of the wild type (WT). The overexpression of ZxZF TFs could alleviate the degree of photoinhibition of photosystems II and I under drought stress and maintain the efficiency of light energy capture and the photosynthetic electron transport chain. The transcriptomic data also showed that differentially expressed genes between the transgenic poplar and WT under drought stress were primarily enriched in metabolic pathways related to photosynthesis, such as photosynthesis, photosynthesis-antenna protein, porphyrin and chlorophyll metabolism, and photosynthetic carbon fixation, and the downregulation of genes related to chlorophyll synthesis, photosynthetic electron transport and Calvin cycle were alleviated. In addition, the overexpression of ZxZF TF can alleviate the inhibition of NADH dehydrogenase-like (NDH) cyclic electron flow of the poplar NDH pathway under drought stress, which plays an important role in reducing the excess pressure of electrons on the photosynthetic electron transport chain and maintaining the normal photosynthetic electron transport. In summary, the overexpression of ZxZF TFs can effectively alleviate the inhibition of drought on the assimilation of carbon in poplar and have a positive impact on light energy capture, the orderly transport of photosynthetic electron transport chain and the integrity of the photosystem, which is highly significant to acheivean in-depth understanding of the function of ZxZF TFs. This also provides an important basis for the breeding of new transgenic poplar varieties.

ABSCISIC ACID INSENSITIVE 4 coordinates eoplast formation to ensure acquisition of seed longevity during maturation in Medicago truncatula

Seed longevity, the capacity to remain alive during dry storage, is pivotal to germination performance and is essential for preserving genetic diversity. It is acquired during late maturation concomitantly with seed degreening and the de-differentiation of chloroplasts into colorless, non-photosynthetic plastids, called eoplasts. As chlorophyll retention leads to poor seed performance upon sowing, these processes are important for seed vigor. However, how these processes are regulated and connected to the acquisition of seed longevity remains poorly understood. Here, we show that such a role is at least provided by ABSCISIC ACID INSENSITIVE 4 (ABI4) in the legume Medicago truncatula. Mature seeds of Mtabi4 mutants contained more chlorophyll than wild-type seeds and exhibited a 75% reduction in longevity and reduced dormancy. MtABI4 was necessary to stimulate eoplast formation, as evidenced by the significant delay in the dismantlement of photosystem II during the maturation of mutant seeds. Mtabi4 seeds also exhibited transcriptional deregulation of genes associated with retrograde signaling and transcriptional control of plastid-encoded genes. Longevity was restored when Mtabi4 seeds developed in darkness, suggesting that the shutdown of photosynthesis during maturation, rather than chlorophyll degradation per se, is a requisite for the acquisition of longevity. Indeed, the shelf life of stay green mutant seeds that retained chlorophyll was not affected. Thus, ABI4 plays a role in coordinating the dismantlement of chloroplasts during seed development to avoid damage that compromises the acquisition of seed longevity. Analysis of Mtabi4 Mtabi5 double mutants showed synergistic effects on chlorophyll retention and longevity, suggesting that they act via parallel pathways.

Uninterrupted embryonic growth leading to viviparous propagule formation in woody mangrove

Vivipary is a rare sexual reproduction phenomenon where embryos germinate directly on the maternal plants. However, it is a common genetic event of woody mangroves in the Rhizophoraceae family. The ecological benefits of vivipary in mangroves include the nurturing of seedlings in harsh coastal and saline environments, but the genetic and molecular mechanisms of vivipary remain unclear. Here we investigate the viviparous embryo development and germination processes in mangrove Kandelia obovata by a transcriptomic approach. Many key biological pathways and functional genes were enriched in different tissues and stages, contributing to vivipary. Reduced production of abscisic acid set a non-dormant condition for the embryo to germinate directly. Genes involved in the metabolism of and response to other phytohormones (gibberellic acid, brassinosteroids, cytokinin, and auxin) are expressed precociously in the axis of non-vivipary stages, thus promoting the embryo to grow through the seed coat. Network analysis of these genes identified the central regulatory roles of LEC1 and FUS3, which maintain embryo identity in Arabidopsis. Moreover, photosynthesis related pathways were significantly up-regulated in viviparous embryos, and substance transporter genes were highly expressed in the seed coat, suggesting a partial self-provision and maternal nursing. We conclude that the viviparous phenomenon is a combinatorial result of precocious loss of dormancy and enhanced germination potential during viviparous seed development. These results shed light on the relationship between seed development and germination, where the continual growth of the embryo replaces a biphasic phenomenon until a mature propagule is established.

Transcriptome and Metabolome Analysis of a Late-Senescent Vegetable Soybean during Seed Development Provides New Insights into Degradation of Chlorophyll

(1) Background: Senescence represents the final stage of plant growth and development, which transfers nutrients to growing seeds and directly affects the yield and quality of crops. However, little is known about chlorophyll degradation in developing and maturing seeds, in contrast to leaf senescence; (2) Methods: RNA-Seq was used to analyze the differentially expressed genes of different late-senescent germplasms. A widely untargeted metabolic analysis was used to analyze differential metabolites. In addition, qRT-PCR was conducted to detect gene expression levels; (3) Results: Transcriptome analysis revealed that ZX12 seeds have a higher expression level of the chlorophyll synthesis genes in the early stage of maturity, compared with ZX4, and have a lower expression level of chlorophyll degradation genes in the late stage of maturity. Flavonoids were the primary differential metabolites, and ZX12 contains the unique and highest expression of three types of metabolites, including farrerol-7-O-glucoside, cyanidin-3-o-(6'-o-feruloyl) glucoside, and kaempferide-3-o-(6'-malonyl) glucoside. Among them, farrerol-7-O-glucoside and cyanidin-3-o-(6'-o-feruloyl) glucoside are flavonoid derivatives containing mono and dihydroxy-B-ring chemical structures, respectively; and (4) Conclusions: It is speculated that the two metabolites can slow down the degradation process of chlorophyll by scavenging oxygen-free radicals in the chloroplast.

New insights into the role of melatonin in photosynthesis

There are numerous studies on enhancing plant resistance to stress using melatonin, but few studies about its effect on photosynthesis. Herein, we summarized the role of melatonin in photosynthesis. Melatonin regulates chlorophyll synthesis and degradation through the transcription of related genes and hormone signals. It protects photosynthetic proteins and maintains the photosynthetic process through improving the transcription of photosystem genes, activating the antioxidant system, and promoting the xanthophyll cycle. Melatonin potentially regulates plant stomatal movement through CAND2/PMTR1. Finally, it controls the photosynthetic carbon cycle by regulating the metabolism of sugar, the gluconeogenesis pathway, and the degradation and transport of transient starch.

SK, Sheoran S, K. UB, K. BN, Kumar S, Singh AN, Singh HV. Seed Longevity in Legumes: Deeper Insights Into Mechanisms and Molecular Perspectives

Sustainable agricultural production largely depends upon the viability and longevity of high-quality seeds during storage. Legumes are considered as rich source of dietary protein that helps to ensure nutritional security, but associated with poor seed longevity that hinders their performance and productivity in farmer's fields. Seed longevity is the key determinant to assure proper seed plant value and crop yield. Thus, maintenance of seed longevity during storage is of prime concern and a pre-requisite for enhancing crop productivity of legumes. Seed longevity is significantly correlated with other seed quality parameters such as germination, vigor, viability and seed coat permeability that affect crop growth and development, consequently distressing crop yield. Therefore, information on genetic basis and regulatory networks associated with seed longevity, as well as molecular dissection of traits linked to longevity could help in developing crop varieties with good storability. Keeping this in view, the present review focuses towards highlighting the molecular basis of seed longevity, with special emphasis on candidate genes and proteins associated with seed longevity and their interplay with other quality parameters. Further, an attempt was made to provide information on 3D structures of various genetic loci (genes/proteins) associated to seed longevity that could facilitate in understanding the interactions taking place within the seed at molecular level. This review compiles and provides information on genetic and genomic approaches for the identification of molecular pathways and key players involved in the maintenance of seed longevity in legumes, in a holistic manner. Finally, a hypothetical fast-forward breeding pipeline has been provided, that could assist the breeders to successfully develop varieties with improved seed longevity in legumes.

Seed-to-Seedling Transition in Pisum sativum L.: A Transcriptomic Approach

The seed-to-seedling transition is a crucial step in the plant life cycle. The transition occurs at the end of seed germination and corresponds to the initiation of embryonic root growth. To improve our understanding of how a seed transforms into a seedling, we germinated the Pisum sativum L. seeds for 72 h and divided them into samples before and after radicle protrusion. Before radicle protrusion, seeds survived after drying and formed normally developed seedlings upon rehydration. Radicle protrusion increased the moisture content level in seed axes, and the accumulation of ROS first generated in the embryonic root and plumule. The water and oxidative status shift correlated with the desiccation tolerance loss. Then, we compared RNA sequencing-based transcriptomics in the embryonic axes isolated from pea seeds before and after radicle protrusion. We identified 24,184 differentially expressed genes during the transition to the post-germination stage. Among them, 2101 genes showed more prominent expression. They were related to primary and secondary metabolism, photosynthesis, biosynthesis of cell wall components, redox status, and responses to biotic stress. On the other hand, 415 genes showed significantly decreased expression, including the groups related to water deprivation (eight genes) and response to the ABA stimulus (fifteen genes). We assume that the water deprivation group, especially three genes also belonging to ABA stimulus (LTI65, LTP4, and HVA22E), may be crucial for the desiccation tolerance loss during a metabolic switch from seed to seedling. The latter is also accompanied by the suppression of ABA-related transcription factors ABI3, ABI4, and ABI5. Among them, HVA22E, ABI4, and ABI5 were highly conservative in functional domains and showed homologous sequences in different drought-tolerant species. These findings elaborate on the critical biochemical pathways and genes regulating seed-to-seedling transition.

Transition from Seeds to Seedlings: Hormonal and Epigenetic Aspects

Transition from seed to seedling is one of the critical developmental steps, dramatically affecting plant growth and viability. Before plants enter the vegetative phase of their ontogenesis, massive rearrangements of signaling pathways and switching of gene expression programs are required. This results in suppression of the genes controlling seed maturation and activation of those involved in regulation of vegetative growth. At the level of hormonal regulation, these events are controlled by the balance of abscisic acid and gibberellins, although ethylene, auxins, brassinosteroids, cytokinins, and jasmonates are also involved. The key players include the members of the LAFL network-the transcription factors LEAFY COTYLEDON1 and 2 (LEC 1 and 2), ABSCISIC ACID INSENSITIVE3 (ABI3), and FUSCA3 (FUS3), as well as DELAY OF GERMINATION1 (DOG1). They are the negative regulators of seed germination and need to be suppressed before seedling development can be initiated. This repressive signal is mediated by chromatin remodeling complexes-POLYCOMB REPRESSIVE COMPLEX 1 and 2 (PRC1 and PRC2), as well as PICKLE (PKL) and PICKLE-RELATED2 (PKR2) proteins. Finally, epigenetic methylation of cytosine residues in DNA, histone post-translational modifications, and post-transcriptional downregulation of seed maturation genes with miRNA are discussed. Here, we summarize recent updates in the study of hormonal and epigenetic switches involved in regulation of the transition from seed germination to the post-germination stage.

Desiccation Tolerance as the Basis of Long-Term Seed Viability

Desiccation tolerance appeared as the key adaptation feature of photoautotrophic organisms for survival in terrestrial habitats. During the further evolution, vascular plants developed complex anatomy structures and molecular mechanisms to maintain the hydrated state of cell environment and sustain dehydration. However, the role of the genes encoding the mechanisms behind this adaptive feature of terrestrial plants changed with their evolution. Thus, in higher vascular plants it is restricted to protection of spores, seeds and pollen from dehydration, whereas the mature vegetative stages became sensitive to desiccation. During maturation, orthodox seeds lose up to 95% of water and successfully enter dormancy. This feature allows seeds maintaining their viability even under strongly fluctuating environmental conditions. The mechanisms behind the desiccation tolerance are activated at the late seed maturation stage and are associated with the accumulation of late embryogenesis abundant (LEA) proteins, small heat shock proteins (sHSP), non-reducing oligosaccharides, and antioxidants of different chemical nature. The main regulators of maturation and desiccation tolerance are abscisic acid and protein DOG1, which control the network of transcription factors, represented by LEC1, LEC2, FUS3, ABI3, ABI5, AGL67, PLATZ1, PLATZ2. This network is complemented by epigenetic regulation of gene expression via methylation of DNA, post-translational modifications of histones and chromatin remodeling. These fine regulatory mechanisms allow orthodox seeds maintaining desiccation tolerance during the whole period of germination up to the stage of radicle protrusion. This time point, in which seeds lose desiccation tolerance, is critical for the whole process of seed development.

A blueberry MIR156a-SPL12 module coordinates the accumulation of chlorophylls and anthocyanins during fruit ripening

Color change is an important event during fruit maturation in blueberry, usually depending on chlorophyll degradation and anthocyanin accumulation. MicroRNA156 (miR156)-SPL modules are an important group of regulatory hubs involved in the regulation of anthocyanin biosynthesis. However, little is known regarding their roles in blueberry or in chlorophyll metabolism during color change. In this study, a MIR156 gene (VcMIR156a) was experimentally identified in blueberry (Vaccinium corymbosum). Overexpression of VcMIR156a in tomato (Solanum lycopersicum) enhanced anthocyanin biosynthesis and chlorophyll degradation in the stem by altering pigment-associated gene expression. Further investigation indicated that the VcSPL12 transcript could be targeted by miR156, and showed the reverse accumulation patterns during blueberry fruit development and maturation. Noticeably, VcSPL12 was highly expressed at green fruit stages, while VcMIR156a transcripts mainly accumulated at the white fruit stage when expression of VcSPL12 was dramatically decreased, implying that VcMIR156a-VcSPL12 is a key regulatory hub during fruit coloration. Moreover, VcSPL12 decreased the expression of several anthocyanin biosynthetic and regulatory genes, and a yeast two-hybrid assay indicated that VcSPL12 interacted with VcMYBPA1. Intriguingly, expression of VcSPL12 significantly enhanced chlorophyll accumulation and altered the expression of several chlorophyll-associated genes. Additionally, the chloroplast ultrastructure was altered by the expression of VcMIR156a and VcSPL12. These findings provide a novel insight into the functional roles of miR156-SPLs in plants, especially in blueberry fruit coloration.

Comprehensive Transcriptomic Analysis for Developing Seeds of a Synthetic Brassica Hexaploid

Polyploidization is a universal phenomenon in plants and plays a crucial role in evolution. In this study, the transcriptomes of developing seeds of a synthetic Brassica hexaploid and its parents (B. rapa and B. carinata) were analyzed to find the gene expression changes in hexaploid seeds. There were 3166 and 3893 DEGs between the Brassica hexaploid and its parents at the full-size stage and mature stage, respectively, most of which were upregulated in hexaploid seeds compared to its parents. At the mature stage, the hexaploid seeds showed a greater difference from its parents. These DEGs had a wide range of functions, which may account for the physiological and morphological differences between the Brassica hexaploid and its parents. The KEGG pathway analysis revealed that hexaploid seeds had higher levels of expression of genes involved in metabolic pathways, RNA transport and biosynthesis of secondary metabolites, and the expression levels in the photosynthesis-related pathways were significantly higher than those in B. rapa. Transgressive expression was the main non-additive expression pattern of the Brassica hexaploid. The gene expression difference between the Brassica hexaploid and its paternal parent was more significant than that with its maternal parent, which may be due in part to the cytoplasmic and maternal effects. Moreover, transcription factor genes, such as G2-like, MYB and mTERF, were highly expressed in hexaploid seeds, possibly promoting their resistance to stress. Our results may provide valuable insights into the adaptation mechanisms of polyploid plants.

Comparative analysis of the plastid conversion, photochemical activity and chlorophyll degradation in developing embryos of green-seeded and yellow-seeded pea (Pisum sativum) cultivars

Developing seeds of some higher plants are photosynthetically active and contain chlorophylls (Chl), which are typically destroyed at the late stages of seed maturation. However, in some crop plant cultivars, degradation of embryonic Chl remains incomplete, and mature seeds preserve green colour, as it is known for green-seeded cultivars of pea (Pisum sativum L.). The residual Chl compromise seed quality and represent a severe challenge for farmers. Hence, comprehensive understanding of the molecular mechanisms, underlying incomplete Chl degradation is required for maintaining sustainable agriculture. Therefore, here we address dynamics of plastid conversion and photochemical activity alterations, accompanying degradation of Chl in embryos of yellow- and green-seeded cultivars Frisson and Rondo respectively. The yellow-seeded cultivar demonstrated higher rate of Chl degradation at later maturation stage, accompanied with termination of photochemical activity, seed dehydration and conversion of green plastids into amyloplasts. In agreement with this, expression of genes encoding enzymes of Chl degradation was lower in the green seeded cultivar, with the major differences in the levels of Chl b reductase (NYC1) and pheophytinase (PPH) transcripts. Thus, the difference between yellow and green seeds can be attributed to incomplete Chl degradation in the latter at the end of maturation period.

Photosynthesis in non-foliar tissues: implications for yield

Photosynthesis is currently a focus for crop improvement. The majority of this work has taken place and been assessed in leaves, and limited consideration has been given to the contribution that other green tissues make to whole-plant carbon assimilation. The major focus of this review is to evaluate the impact of non-foliar photosynthesis on carbon-use efficiency and total assimilation. Here we appraise and summarize past and current literature on the substantial contribution of different photosynthetically active organs and tissues to productivity in a variety of different plant types, with an emphasis on fruit and cereal crops. Previous studies provide evidence that non-leaf photosynthesis could be an unexploited potential target for crop improvement. We also briefly examine the role of stomata in non-foliar tissues, gas exchange, maintenance of optimal temperatures and thus photosynthesis. In the final section, we discuss possible opportunities to manipulate these processes and provide evidence that Triticum aestivum (wheat) plants genetically manipulated to increase leaf photosynthesis also displayed higher rates of ear assimilation, which translated to increased grain yield. By understanding these processes, we can start to provide insights into manipulating non-foliar photosynthesis and stomatal behaviour to identify novel targets for exploitation in continuing breeding programmes.

Integrating Optical Imaging Tools for Rapid and Non-invasive Characterization of Seed Quality: Tomato (Solanum lycopersicum L.) and Carrot (Daucus carota L.) as Study Cases

Light-based methods are being further developed to meet the growing demands for food in the agricultural industry. Optical imaging is a rapid, non-destructive, and accurate technology that can produce consistent measurements of product quality compared to conventional techniques. In this research, a novel approach for seed quality prediction is presented. In the proposed approach two advanced optical imaging techniques based on chlorophyll fluorescence and chemometric-based multispectral imaging were employed. The chemometrics encompassed principal component analysis (PCA) and quadratic discrimination analysis (QDA). Among plants that are relevant as both crops and scientific models, tomato, and carrot were selected for the experiment. We compared the optical imaging techniques to the traditional analytical methods used for quality characterization of commercial seedlots. Results showed that chlorophyll fluorescence-based technology is feasible to discriminate cultivars and to identify seedlots with lower physiological potential. The exploratory analysis of multispectral imaging data using a non-supervised approach (two-component PCA) allowed the characterization of differences between carrot cultivars, but not for tomato cultivars. A Random Forest (RF) classifier based on Gini importance was applied to multispectral data and it revealed the most meaningful bandwidths from 19 wavelengths for seed quality characterization. In order to validate the RF model, we selected the five most important wavelengths to be applied in a QDA-based model, and the model reached high accuracy to classify lots with high-and low-vigor seeds, with a correct classification from 86 to 95% in tomato and from 88 to 97% in carrot for validation set. Further analysis showed that low quality seeds resulted in seedlings with altered photosynthetic capacity and chlorophyll content. In conclusion, both chlorophyll fluorescence and chemometrics-based multispectral imaging can be applied as reliable proxies of the physiological potential in tomato and carrot seeds. From the practical point of view, such techniques/methodologies can be potentially used for screening low quality seeds in food and agricultural industries.

Mechanisms Regulating the Dynamics of Photosynthesis Under Abiotic Stresses

Photosynthesis sustains plant life on earth and is indispensable for plant growth and development. Factors such as unfavorable environmental conditions, stress regulatory networks, and plant biochemical processes limits the photosynthetic efficiency of plants and thereby threaten food security worldwide. Although numerous physiological approaches have been used to assess the performance of key photosynthetic components and their stress responses, though, these approaches are not extensive enough and do not favor strategic improvement of photosynthesis under abiotic stresses. The decline in photosynthetic capacity of plants due to these stresses is directly associated with reduction in yield. Therefore, a detailed information of the plant responses and better understanding of the photosynthetic machinery could help in developing new crop plants with higher yield even under stressed environments. Interestingly, cracking of signaling and metabolic pathways, identification of some key regulatory elements, characterization of potential genes, and phytohormone responses to abiotic factors have advanced our knowledge related to photosynthesis. However, our understanding of dynamic modulation of photosynthesis under dramatically fluctuating natural environments remains limited. Here, we provide a detailed overview of the research conducted on photosynthesis to date, and highlight the abiotic stress factors (heat, salinity, drought, high light, and heavy metal) that limit the performance of the photosynthetic machinery. Further, we reviewed the role of transcription factor genes and various enzymes involved in the process of photosynthesis under abiotic stresses. Finally, we discussed the recent progress in the field of biodegradable compounds, such as chitosan and humic acid, and the effect of melatonin (bio-stimulant) on photosynthetic activity. Based on our gathered researched data set, the logical concept of photosynthetic regulation under abiotic stresses along with improvement strategies will expand and surely accelerate the development of stress tolerance mechanisms, wider adaptability, higher survival rate, and yield potential of plant species.

Profiling of Seed Proteome in Pea (Pisum sativum L.) Lines Characterized with High and Low Responsivity to Combined Inoculation with Nodule Bacteria and Arbuscular Mycorrhizal Fungi

Legume crops represent the major source of food protein and contribute to human nutrition and animal feeding. An essential improvement of their productivity can be achieved by symbiosis with beneficial soil microorganisms-rhizobia (Rh) and arbuscular mycorrhizal (AM) fungi. The efficiency of these interactions depends on plant genotype. Recently, we have shown that, after simultaneous inoculation with Rh and AM, the productivity gain of pea (Pisum sativum L) line K-8274, characterized by high efficiency of interaction with soil microorganisms (EIBSM), was higher in comparison to a low-EIBSM line K-3358. However, the molecular mechanisms behind this effect are still uncharacterized. Therefore, here, we address the alterations in pea seed proteome, underlying the symbiosis-related productivity gain, and identify 111 differentially expressed proteins in the two lines. The high-EIBSM line K-8274 responded to inoculation by prolongation of seed maturation, manifested by up-regulation of proteins involved in cellular respiration, protein biosynthesis, and down-regulation of late-embryogenesis abundant (LEA) proteins. In contrast, the low-EIBSM line K-3358 demonstrated lower levels of the proteins, related to cell metabolism. Thus, we propose that the EIBSM trait is linked to prolongation of seed filling that needs to be taken into account in pulse crop breeding programs. The raw data have been deposited to the ProteomeXchange with identifier PXD013479.

Proteome Map of Pea (Pisum sativum L.) Embryos Containing Different Amounts of Residual Chlorophylls

Due to low culturing costs and high seed protein contents, legumes represent the main global source of food protein. Pea (Pisum sativum L.) is one of the major legume crops, impacting both animal feed and human nutrition. Therefore, the quality of pea seeds needs to be ensured in the context of sustainable crop production and nutritional efficiency. Apparently, changes in seed protein patterns might directly affect both of these aspects. Thus, here, we address the pea seed proteome in detail and provide, to the best of our knowledge, the most comprehensive annotation of the functions and intracellular localization of pea seed proteins. To address possible intercultivar differences, we compared seed proteomes of yellow- and green-seeded pea cultivars in a comprehensive case study. The analysis revealed totally 1938 and 1989 nonredundant proteins, respectively. Only 35 and 44 proteins, respectively, could be additionally identified after protamine sulfate precipitation (PSP), potentially indicating the high efficiency of our experimental workflow. Totally 981 protein groups were assigned to 34 functional classes, which were to a large extent differentially represented in yellow and green seeds. Closer analysis of these differences by processing of the data in KEGG and String databases revealed their possible relation to a higher metabolic status and reduced longevity of green seeds.