Cell-type-specific metabolism in plants.

Every plant organ contains tens of different cell types, each with a specialized function. These functions are intrinsically associated with specific metabolic flux distributions that permit the synthesis of the ATP, reducing equivalents and biosynthetic precursors demanded by the cell. Investigating such cell-type-specific metabolism is complicated by the mosaic of different cells within each tissue combined with the relative scarcity of certain types. However, techniques for the isolation of specific cells, their analysis in situ by microscopy, or modeling of their function in silico have permitted insight into cell-type-specific metabolism. In this review we present some of the methods used in the analysis of cell-type-specific metabolism before describing what we know about metabolism in several cell types that have been studied in depth; (i) leaf source and sink cells; (ii) glandular trichomes that are capable of rapid synthesis of specialized metabolites; (iii) guard cells that must accumulate large quantities of the osmolytes needed for stomatal opening; (iv) cells of seeds involved in storage of reserves; and (v) the mesophyll and bundle sheath cells of C4 plants that participate in a CO2 concentrating cycle. Metabolism is discussed in terms of its principal features, connection to cell function and what factors affect the flux distribution. Demand for precursors and energy, availability of substrates and suppression of deleterious processes are identified as key factors in shaping cell-type-specific metabolism.

Alterations in the root phenylpropanoid pathway and root-shoot vessel system as main determinants of the drought tolerance of a soybean genotype.

Climate change increases precipitation variability, particularly in savanna environments. We have used integrative strategies to understand the molecular mechanisms of drought tolerance, which will be crucial for developing improved genotypes. The current study compares the molecular and physiological parameters between the drought-tolerant Embrapa 48 and the sensitive BR16 genotypes. We integrated the root-shoot system's transcriptome, proteome, and metabolome to understand drought tolerance. The results indicated that Embrapa 48 had a greater capacity for water absorption due to alterations in length and volume. Drought tolerance appears to be ABA-independent, and IAA levels in the leaves partially explain the higher root growth. Proteomic profiles revealed up-regulated proteins involved in glutamine biosynthesis and proteolysis, suggesting osmoprotection and explaining the larger root volume. Dysregulated proteins in the roots belong to the phenylpropanoid pathways. Additionally, PR-like proteins involved in the biosynthesis of phenolics may act to prevent oxidative stress and as a substrate for modifying cell walls. Thus, we concluded that alterations in the root-shoot conductive vessel system are critical in promoting drought tolerance. Moreover, photosynthetic parameters from reciprocal grafting experiments indicated that the root system is more essential than the shoots in the drought tolerance mechanism. Finally, we provided a comprehensive overview of the genetic, molecular, and physiological traits involved in drought tolerance mechanisms. Supplementary Information: The online version contains supplementary material available at 10.1007/s12298-023-01307-7.

Anemochorous and zoochorous seeds of trees from the Brazilian savannas differ in fatty acid content and composition.

Fatty acids (FAs) stored as triacylglycerols (TAGs) are an important source of carbon and energy for germination and seedling development, particularly for plants with small wind-dispersed seeds, allowing greater efficiency in storing both energy and carbon. These plants should be under strong selection to produce seeds rich in FAs and with large amounts of saturated FAs. Their closely packed single-chain configuration allows greater packing, more carbon and energy per unit mass, and are less costly to produce. Efficient carbon storage would be less crucial for zoochorous species, which can reach much larger seed sizes (mass). We analysed the transesterified FA profile from seeds of 22 anemochorous and zoochorous tree species from the Cerrado savannas of Central Brazil. We tested if seed FA content covaried with seed mass and if anemochorous and zoochorous seeds differed in FA contents and distribution. Fatty acids were an important seed source of carbon and energy for most species. Fifteen different FAs were identified. Oleic, linoleic and linolenic tended to be the predominant unsaturated FAs. Oleic acid corresponded to more than 60 % of the total transesterified FAs in seeds of Kielmeyera coriacea, Qualea dichotoma and Triplaris americana. Linoleic acid corresponded to more than 50 % of total FA in Dalbergia miscolobium, Parkia platycephala and Ferdinandusa elliptica while linolenic acid was the dominant component in Inga cylindrica. Across species, palmitic and stearic were the dominant saturated FAs. The only exception was lauric acid (68 % of total FA) in seeds of Qualea grandiflora. On a log10 scale, as the seed increased in mass, accumulation of FAs tends to proceed at a faster rate in anemochorous species than in zoochorous species. They also became increasingly richer in saturated FAs. Zoochorous species had seed TAGs with higher proportion of polyunsaturated FAs.

Revealing Corynebacterium glutamicum proteoforms through top-down proteomics.

Corynebacterium glutamicum is a bacterium widely employed in the industrial production of amino acids as well as a broad range of other biotechnological products. The present study describes the characterization of C. glutamicum proteoforms, and their post-translational modifications (PTMs) employing top-down proteomics. Despite previous evidence of PTMs having roles in the regulation of C. glutamicum metabolism, this is the first top-down proteome analysis of this organism. We identified 1125 proteoforms from 273 proteins, with 60% of proteins presenting at least one mass shift, suggesting the presence of PTMs, including several acetylated, oxidized and formylated proteoforms. Furthermore, proteins relevant to amino acid production, protein secretion, and oxidative stress were identified with mass shifts suggesting the presence of uncharacterized PTMs and proteoforms that may affect biotechnologically relevant processes in this industrial workhorse. For instance, the membrane proteins mepB and SecG were identified as a cleaved and a formylated proteoform, respectively. While in the central metabolism, OdhI was identified as two proteoforms with potential biological relevance: a cleaved proteoform and a proteoform with PTMs corresponding to a 70 Da mass shift.

Quinoa for the Brazilian Cerrado: Agronomic Characteristics of Elite Genotypes under Different Water Regimes.

Quinoa stands out as an excellent crop in the Cerrado region for cultivation in the off-season or irrigated winter season. Here, we tested the effects of different water regimes on the agronomic characteristics, physiology, and grain quality of different elite quinoa genotypes under field conditions. The experiment was conducted under field conditions at Embrapa Cerrados (Planaltina, DF, Brazil). The experimental design was in randomized blocks, in a split-plot scheme, with four replications. The plots were composed of 18 quinoa genotypes and modified BRS Piabiru (the currently used genotype), and the split-plots were divided into 4 different water regimes. The following variables were evaluated: productivity and productivity per unit of applied water (PUAA), plant height, flavonoids, anthocyanins, gas exchange, chlorophyll, leaf proline, and relative water content. Our results showed that water regimes between 309 and 389 mm can be recommended for quinoa in the Cerrado region. CPAC6 and CPAC13 presented the highest yield and PUAA under high and intermediate WRs, and hence were the most suitable for winter growth under irrigation. CPAC17 is most suitable for off-season growth under rainfed conditions, as it presented the highest PUAA under the low WRs (247 and 150). CPAC9 stood out in terms of accumulation of flavonoids and anthocyanins in all WRs. Physiological analyses revealed different responses of the genotypes to water restriction, together with symptoms of stress under lower water regimes. Our study reinforces the importance of detailed analyses of the relationship between productivity, physiology, and water use when choosing genotypes for planting and harvest in different seasons.

Contrasting Effects of Wild Arachis Dehydrin Under Abiotic and Biotic Stresses.

Plant dehydrins (DNHs) belong to the LEA (Late Embryogenesis Abundant) protein family and are involved in responses to multiple abiotic stresses. DHNs are classified into five subclasses according to the organization of three conserved motifs (K-; Y-; and S-segments). In the present study, the DHN protein family was characterized by molecular phylogeny, exon/intron organization, protein structure, and tissue-specificity expression in eight Fabaceae species. We identified 20 DHN genes, encompassing three (YnSKn, SKn, and Kn) subclasses sharing similar gene organization and protein structure. Two additional low conserved DHN Φ-segments specific to the legume SKn-type of proteins were also found. The in silico expression patterns of DHN genes in four legume species (Arachis duranensis, A. ipaënsis, Glycine max, and Medicago truncatula) revealed that their tissue-specific regulation is associated with the presence or absence of the Y-segment. Indeed, DHN genes containing a Y-segment are mainly expressed in seeds, whereas those without the Y-segment are ubiquitously expressed. Further qRT-PCR analysis revealed that, amongst stress responsive dehydrins, a SKn-type DHN gene from A. duranensis (AdDHN1) showed opposite response to biotic and abiotic stress with a positive regulation under water deficit and negative regulation upon nematode infection. Furthermore, transgenic Arabidopsis lines overexpressing (OE) AdDHN1 displayed improved tolerance to multiple abiotic stresses (freezing and drought) but increased susceptibility to the biotrophic root-knot nematode (RKN) Meloidogyne incognita. This contradictory role of AdDHN1 in responses to abiotic and biotic stresses was further investigated by qRT-PCR analysis of transgenic plants using a set of stress-responsive genes involved in the abscisic acid (ABA) and jasmonic acid (JA) signaling pathways and suggested an involvement of DHN overexpression in these stress-signaling pathways.

Early responses to dehydration in contrasting wild Arachis species.

Wild peanut relatives (Arachis spp.) are genetically diverse and were selected throughout evolution to a range of environments constituting, therefore, an important source of allelic diversity for abiotic stress tolerance. In particular, A. duranensis and A. stenosperma, the parents of the reference Arachis A-genome genetic map, show contrasting transpiration behavior under limited water conditions. This study aimed to build a comprehensive gene expression profile of these two wild species under dehydration stress caused by the withdrawal of hydroponic nutrient solution. For this purpose, roots of both genotypes were collected at seven time-points during the early stages of dehydration and used to construct cDNA paired-end libraries. Physiological analyses indicated initial differences in gas exchange parameters between the drought-tolerant genotype of A. duranensis and the drought-sensitive genotype of A. stenosperma. High-quality Illumina reads were mapped against the A. duranensis reference genome and resulted in the identification of 1,235 and 799 Differentially Expressed Genes (DEGs) that responded to the stress treatment in roots of A. duranensis and A. stenosperma, respectively. Further analysis, including functional annotation and identification of biological pathways represented by these DEGs confirmed the distinct gene expression behavior of the two contrasting Arachis species genotypes under dehydration stress. Some species-exclusive and common DEGs were then selected for qRT-PCR analysis, which corroborated the in silico expression profiling. These included genes coding for regulators and effectors involved in drought tolerance responses, such as activation of osmosensing molecular cascades, control of hormone and osmolyte content, and protection of macromolecules. This dataset of transcripts induced during the dehydration process in two wild Arachis genotypes constitute new tools for the understanding of the distinct gene regulation processes in these closely related species but with contrasting drought responsiveness. In addition, our findings provide insights into the nature of drought tolerance in wild germoplasm, which might be explored as novel sources of diversity and useful wild alleles to develop climate-resilient crop varieties.