Plant responses to salt stress involve regulatory networks integrating ion transport, hormonal signaling, and root system architecture remodeling. A key adaptive mechanism is the regulation of sodium (Na⁺) transport by Class 1 HKT1 transporters, which compertamentalize Na⁺ in non-photosynthetic tissues. High HKT1 expression reduces Na+ accumulation in shoots, leading to increased salt tolerance, but simultaneously results in reduced lateral root development. In this study, we explored transcriptional responses that are altered by high HKT1 expression in root stelle in two Arabidopsis backgrounds, Col-0 and C24. We identified TMAC2, a negative ABA regulator, and TIP2:2, a tonoplast aquaporin, as key modulators of root development under salt stress. While TIP2:2 function was conserved, TMAC2 exhibited genotype-specific effects on ABA accumulation and HKT1-mediated salt sensitivity. Co-expression of TMAC2 and HKT1 in Col-0 upregulated ABI4 and ABI5, linking Na⁺ transport to ABA signaling. Our findings underscore genetic context in shaping salt responses and provide molecular targets for enhancing root plasticity under stress.

Plant responses to salt stress involve complex processes integrating short- and long-term adaptations, including changes in ion transport, systemic signaling, root architecture, and biomass distribution. A key adaptive mechanism involves the regulation of sodium (Na+) and potassium (K+) ion transport via Class 1 HKT1 transporters, which reduce Na+ accumulation in shoots, thereby enhancing salinity tolerance but at the expense of lateral root development. In this study, we identified differential roles of TMAC2 in modulating ABA accumulation and lateral root development under salt stress in two distinct Arabidopsis genotypes, Col-0 and C24. Overexpression of TMAC2 in the Col-0 background increased ABA accumulation, resulting in reduced lateral root development, suggesting a positive feedback loop involving HKT1, TMAC2, and ABA signaling. In contrast, TMAC2 overexpression in C24 reduced ABA accumulation in lines overexpressing HKT1, indicating genotype-specific differences in the TMAC2-HKT1 interaction. Additionally, we observed that the co-expression of TMAC2 and HKT1 in Col-0 induced ABI4 and ABI5 transcription factors, which are known to mediate salt sensitivity. These findings reveal a regulatory network where TMAC2 and HKT1 modulate salt stress responses through genotype-dependent feedback mechanisms. Our results highlight the complexity of root remodeling under salt stress and the crucial role of genetic background in shaping these adaptive responses. ### Competing Interest Statement The authors have declared no competing interest.

Quinoa (Chenopodium quinoa) is an important crop for the future challenges of food and nutrient security. Deep characterization of quinoa diversity is needed to support the agronomic improvement and adaptation of quinoa as its worldwide cultivation expands. In this study, we report the construction of chromosome-scale genome assemblies of eight quinoa accessions covering the range of phenotypic and genetic diversity of both lowland and highland quinoas. The assemblies were produced from a combination of PacBio HiFi reads and Bionano Saphyr optical maps, with total assembly sizes averaging 1.28 Gb with a mean N50 of 71.1 Mb. Between 43,733 and 48,564 gene models were predicted for the eight new quinoa genomes, and on average, 66% of each quinoa genome was classified as repetitive sequences. Alignment between the eight genome assemblies allowed the identification of structural rearrangements including inversions, translocations, and duplications. These eight novel quinoa genome assemblies provide a resource for association genetics, comparative genomics, and pan-genome analyses for the discovery of genetic components and variations underlying agriculturally important traits.

Soil salinity is a major environmental stressor affecting agricultural productivity worldwide. Understanding plant responses to salt stress is crucial for developing resilient crop varieties. Wild relatives of cultivated crops, such as wild tomato, Solanum pimpinellifolium, can serve as a useful resource to further expand the resilience potential of the cultivated germplasm, S. lycopersicum. In this study, we employed high-throughput phenotyping in the greenhouse and field conditions to explore salt stress responses of a S. pimpinellifolium diversity panel. Our study revealed extensive phenotypic variations in response to salt stress, with traits such as transpiration rate, shoot mass, and ion accumulation showing significant correlations with plant performance. We found that while transpiration was a key determinant of plant performance in the greenhouse, shoot mass strongly correlated with yield under field conditions. Conversely, ion accumulation was the least influential factor under greenhouse conditions. Through a Genome Wide Association Study, we identified candidate genes not previously associated with salt stress, highlighting the power of high-throughput phenotyping in uncovering novel aspects of plant stress responses. This study contributes to our understanding of salt stress tolerance in S. pimpinellifolium and lays the groundwork for further investigations into the genetic basis of these traits, ultimately informing breeding efforts for salinity tolerance in tomato and other crops.

AbstractSoil salinity is a major environmental stressor affecting agricultural productivity worldwide. Understanding plant responses to salt stress is crucial for developing resilient crop varieties. Wild relatives of cultivated crops, such as wild tomato,Solanum pimpinellifolium, can serve as a useful resource to further expand the resilience potential of the cultivated germplasm,S. lycopersicum. In this study, we employed high-throughput phenotyping in the greenhouse and field conditions to explore salt stress responses of aS. pimpinellifoliumdiversity panel. Our study revealed extensive phenotypic variations in response to salt stress, with traits such as transpiration rate, shoot mass, and ion accumulation showing significant correlations with plant performance. We found that while transpiration was a key determinant of plant performance in the greenhouse, shoot mass strongly correlated with yield under field conditions. Conversely, ion accumulation was the least influential factor under greenhouse conditions. Through a Genome Wide Association Study, we identified candidate genes not previously associated with salt stress, highlighting the power of high-throughput phenotyping in uncovering novel aspects of plant stress responses. This study contributes to our understanding of salt stress tolerance inS. pimpinellifoliumand lays the groundwork for further investigations into the genetic basis of these traits, ultimately informing breeding efforts for salinity tolerance in tomato and other crops.

Salt stress decreases plant growth prior to significant ion accumulation in the shoot. However, the processes underlying this rapid reduction in growth are still unknown. To understand the changes in salt stress responses through time and at multiple physiological levels, examining different plant processes within a single setup is required. Recent advances in phenotyping has allowed the image-based estimation of plant growth, morphology, colour and photosynthetic activity. In this study, we examined the salt stress-induced responses of 191 Arabidopsis accessions from one hour to seven days after treatment using high-throughput phenotyping. Multivariate analyses and machine learning algorithms identified that quantum yield measured in the light-adapted state (Fv′/Fm′) greatly affected growth maintenance in the early phase of salt stress, while maximum quantum yield (QY max) was crucial at a later stage. In addition, our genome-wide association study (GWAS) identified 770 loci that were specific to salt stress, in which two loci associated with QY max and Fv′/Fm′ were selected for validation using T-DNA insertion lines. We characterised an unknown protein kinase found in the QY max locus, which reduced photosynthetic efficiency and growth maintenance under salt stress. Understanding the molecular context of the identified candidate genes will provide valuable insights into the early plant responses to salt stress. Furthermore, our work incorporates high-throughput phenotyping, multivariate analyses and GWAS, uncovering details of temporal stress responses, while identifying associations across different traits and time points, which likely constitute the genetic components of salinity tolerance.

Chenopodium quinoa (quinoa) is a highly nutritious grain identified as an important crop to improve world food security. Unfortunately, few resources are available to facilitate its genetic improvement. Here we report the assembly of a high-quality, chromosome-scale reference genome sequence for quinoa, which was produced using single-molecule real-time sequencing in combination with optical, chromosome-contact and genetic maps. We also report the sequencing of two diploids from the ancestral gene pools of quinoa, which enables the identification of sub-genomes in quinoa, and reduced-coverage genome sequences for 22 other samples of the allotetraploid goosefoot complex. The genome sequence facilitated the identification of the transcription factor likely to control the production of anti-nutritional triterpenoid saponins found in quinoa seeds, including a mutation that appears to cause alternative splicing and a premature stop codon in sweet quinoa strains. These genomic resources are an important first step towards the genetic improvement of quinoa.

Nature 542, 307–312 (2017); doi:10.1038/nature21370 The Acknowledgements section of this Article should have included the following sentence: “Metabolite imaging was conducted at Metabolomics Australia (School of BioSciences, The University of Melbourne, Australia), a NCRIS initiative under Bioplatforms Australia Pty Ltd.