Cold-acclimation is essential for the development of adequate frost-hardiness in cereals and therefore sudden freezes can cause considerable damage to the canopy. However, timely adding of an appropriate signal in the absence of cold acclimation may also harden wheat for the upcoming freeze. The feasibility of the promising signal molecule methylglyoxal was tested here for such applications and the signal mechanism was studied in bread wheat (Triticum aestivum L.) and durum wheat (Triticum turgidum L. ssp. durum). Spraying with 10 mM methylglyoxal did not decrease the fresh weight and photosynthetic parameters in most wheat varieties at growth temperature (21 °C). Photosynthetic parameters even improved and chlorophyll content increased in some cases. Increased transcript level of glutathione-S-transferases and omega-3 fatty acid desaturases was detected by qPCR 6 h after the last methylglyoxal spray. Aldo-keto reductase and glyoxalase enzyme activities, as well as sorbitol content of wheat plants increased 24 h after the last 10 mM methylglyoxal spray in most of the cultivars. These mechanisms may explain the increased freezing survival of methylglyoxal pretreated wheat plants from less than 10% to over 30%. Our results demonstrate that exogenous methylglyoxal treatment can be safely added to wheat plants as preparatory treatment without detrimental effects but inducing some of the stress-protective mechanisms, which contribute to frost-hardiness.

Root-based uptake of inorganic carbon has been suggested as an additional carbon source. Our study aimed to characterize and understand the root-based uptake and fixation mechanisms and their impact on plant growth. ¹³C-labeled bicarbonate fed to Arabidopsis roots was assimilated into aspartic acid but mainly into sucrose, indicating that the added inorganic carbon was transported to the leaves. A hydroponic treatment was also established for A. thaliana using 2 mM NaHCO₃ at pH 5.6, which enhanced the photosynthetic and growth parameters. According to transcriptome sequencing data, the observed enhancement in growth may be orchestrated by trehalose-6-phosphate signaling and supported by augmented nitrogen and sulfur assimilation. The analysis also revealed regulatory and transporter activities, including several nitrate (NRT2.1), and sulfate transporter (SULTR1;1 and SULTR1;2) candidates that could participate in bicarbonate uptake. Different transporters and carbon fixation mutants were assessed. Arabidopsis homologs of SLOW-TYPE ANION CHANNEL 1 (slah3) CARBONIC ANHYDRASE (βca4), and SULFATE TRANSPORTER (sultr1;2) mutants were shown to be inferior to the bicarbonate-treated wild types in several growth and root ultrastructural parameters. Besides, aquaporin genes PIP1;3 and PIP2;6 could play a negative role in the carbon uptake by venting carbon dioxide out of the plant. The findings support the hypothesis that the inorganic carbon is taken up by the root anion channels, mostly transported up to the shoots by the xylem, and fixed there by RuBisCo after the conversion to CO₂ by carbonic anhydrases. The process boosts photosynthesis and growth by providing an extra carbon supply.

High molecular weight glutenin subunits (HMW GS) represent an important fraction of endosperm-specific seed-storage proteins that provide elasticity to bread dough. Previously, the second cis-regulatory module (CRM2) was found to be one of the most conserved part of HMW GS promoters, which indicated its pre-eminent role in their gene regulation. Here, we observed that deletion of CRM2 from the promoters of the Bx7 and By8 HMW GS genes increased the leakage of their transient expression in wheat leaf tissue. The effect of a VP1, an Myb and an antisense bZIP transcription factor (TF)-binding site, potentially involved in endosperm-specific regulation within CRM2, was then studied. The activity of a Bx7 gene promoter containing a mutant CRM2 with altered VP1 and Myb TF-binding sites, but an intact bZIP TF-binding site, was similarly low to that of the wild type in leaves. Transactivation analysis and EMSA indicated the binding of TFs TabZIP34 and TabZIP115 to the Skn-1 motif GTCAT in CRM2 and the repression of Bx7 and By8 HMW GS gene promoter activity in leaves. TabZIP34 and TabZIP115 may be involved in the downregulation of HMW GS gene expression in vegetative tissues and early-stage endosperm as well its modulation during seed maturation.

Polyphenol oxidases (PPOs) play a pivotal role in plant immune responses by catalysing the oxidation of phenolic compounds into cytotoxic quinones and melanin and contributing to the fortification of cell walls. Despite their biological significance, the high expression of PPOs in potatoes is not desirable due to their promotion of tuber browning. This study elucidates the relationship between PPO activity and defense mechanisms against the diverse pathogens Ralstonia solanacearum (Rs) and Phytophthora infestans (Pi) while mitigating enzymatic browning. CRISPR/Cas-mediated editing of the tuber- and root-specific PPO genes in the 'Désirée' and 'Balatoni Rózsa' potato cultivars considerably reduced enzymatic activity and browning. Among four PPO-edited mutant lines, three exhibited increased susceptibility to Rs while responses to Pi remained unchanged, underscoring the importance of PPOs in resistance to Rs. The PPO knockouts resulted in significant shifts in metabolite and hormone profiles characterized by elevated levels of dihydrokaempferol, coniferyl alcohol and taxifolin among other metabolites in the roots of Rs-susceptible mutants. Additionally, reduced PPO activity in these lines correlated with increased concentrations of salicylic acid, jasmonic acid and several antimicrobial compounds and alterations in flavonoid regulation. These findings highlight the complex role of PPOs in plant defense, establishing a positive correlation between PPO activity and resistance to Rs, while offering insights into the trade-offs associated with PPO gene editing in potatoes.

Background and Aims: This study aimed to elucidate the mechanisms of root-based inorganic carbon (RIC) uptake and fixation in Arabidopsis thaliana and barley ( Hordeum vulgare ‘Golden Promise’) and compare the physiological response of the two species under osmotic stress. Methods: Barley plants were grown in a growth-promoting inorganic carbon (IC)-containing hydroponic solution. Analyses included fluxomics, physiological measurements, amino acid profiling in leaves, and RNA sequencing. PEG-induced osmotic stress assays were performed for barley and Arabidopsis. Fixation of ¹³ C-labelled carbon into shoot dry mass was studied for Arabidopsis thaliana genotypes Col and high suberin-producing mutants sultr1;2 and esb1-1. Results: IC treatment improved barley growth and net photosynthesis, though the effects were less pronounced than in Arabidopsis. In barley, IC fixation occurred mainly in roots via phosphoenolpyruvate carboxylase (PEPC), supported by fluxomic and transcriptome data. The high suberin-producing Arabidopsis mutants took up and fixed less ¹³ C from the hydroponic solution, but no change of suberin-related pathways was observed in the transcriptome of IC-treated barley. Amino acid profiling and transcriptomics in barley leaves revealed an increased use of pyruvate-derived amino acids (leucine, alanine, valine, and isoleucine), supporting protein synthesis and photosynthesis. In the leaves, genes related to cell division and cell expansion, and chloroplast biosynthesis were upregulated. Under PEG-induced osmotic stress, IC-supplementation improved the growth of Arabidopsis and some photosynthetic parameters of barley. Conclusions: The observed growth promotion in barley under root-IC treatment is driven by carbon uptake and fixation pathways that differ significantly from the mechanisms utilized by Arabidopsis.

Grain yield is a complex trait determined by multiple genes, physiological and developmental processes, including those governed by cytoskeletal dynamics. In this study, we investigated the role of the TONNEAU 1b (TON1b) gene, a core component of the TON1-TRM-PP2A (TTP) complex involved in microtubule organization and cell division plane positioning, in the polyploid context of durum wheat (Triticum turgidum ssp. durum). To explore its function and agronomic potential, we developed intragenic Svevo lines overexpressing TON1b under the control of the endosperm-specific 1Dx5 promoter, using a CRE-LOX recombination system to produce marker-free genotypes. Molecular and phenotypic analyses of fixed intragenic lines revealed significant increases in grain length, grain weight, spikelet number and total starch content, without compromising grain number per spike. Transcriptomic profiling indicated consistent TON1b overexpression alongside downregulation of CEN1 and TON2, and upregulation of GW7, suggesting a regulatory role in both cell division and elongation processes. These findings suggest a role of TON1b on cytoskeletal remodelling and grain development, offering a promising genetic lever for yield improvement in durum wheat.