Soil salinization is an important factor limiting food security and ecological stability. As a commonly used greening tree species, Robinia pseudoacacia often suffers from salt stress that can manifest as leaf yellowing, decreased photosynthesis, disintegrated chloroplasts, growth stagnation, and even death. To elucidate how salt stress decreases photosynthesis and damages photosynthetic structures, we treated R. pseudoacacia seedlings with different concentrations of NaCl (0, 50, 100, 150, and 200 mM) for 2 weeks and then measured their biomass, ion content, organic soluble substance content, reactive oxygen species (ROS) content, antioxidant enzyme activity, photosynthetic parameters, chloroplast ultrastructure, and chloroplast development-related gene expression. NaCl treatment significantly decreased biomass and photosynthetic parameters, but increased ion content, organic soluble substances, and ROS content. High NaCl concentrations (100–200 mM) also led to distorted chloroplasts, scattered and deformed grana lamellae, disintegrated thylakoid structures, irregularly swollen starch granules, and larger, more numerous lipid spheres. Compared to control (0 mM NaCl), the 50 mM NaCl treatment significantly increased antioxidant enzyme activity while upregulating the expression of the ion transport-related genes Na⁺/H⁺ exchanger 1(NHX 1) and salt overly sensitive 1 (SOS 1) and the chloroplast development-related genes psaA, psbA, psaB, psbD, psaC, psbC, ndhH, ndhE, rps7, and ropA. Additionally, high concentrations of NaCl (100–200 mM) decreased antioxidant enzyme activity and downregulated the expression of ion transport- and chloroplast development-related genes. These results showed that although R. pseudoacacia can tolerate low concentrations of NaCl, high concentrations (100–200 mM) can damage chloroplast structure and disturb metabolic processes by downregulating gene expression.

SUMOylation increases the protein stability of DREB2A, a key transcription factor in the response to heat stress in plant cells.

The circadian clock regulates plant tissue hydraulics to synchronize water supply with environmental cycles and thereby optimize growth. The circadian fluctuations in aquaporin transcript abundance suggest that aquaporin water channels play a role in these processes. Here, we show that hydraulic conductivity (K_ros) of Arabidopsis (Arabidopsis thaliana) rosettes displays a genuine circadian rhythmicity with a peak around midday. Combined immunological and proteomic approaches revealed that phosphorylation at two C-terminal sites (Ser280, Ser283) of PLASMA MEMBRANE INTRINSIC PROTEIN 2;1 (AtPIP2;1), a major plasma membrane aquaporin in rosettes, shows circadian oscillations and is correlated with K_ros. Transgenic expression of phosphodeficient and phosphomimetic forms of this aquaporin indicated that AtPIP2;1 phosphorylation is necessary but not sufficient for K_ros regulation. We investigated the supporting role of 14-3-3 proteins, which are known to interact with and regulate phosphorylated proteins. Individual knockout plants for five 14-3-3 protein isoforms expressed in rosettes lacked circadian activation of K_ros. Two of these [GRF4 (14-3-3Phi); GRF10 (14-3-3Epsilon)] showed direct interactions with AtPIP2;1 in the plant and upon coexpression in Xenopus laevis oocytes and activated AtPIP2;1, preferentially when the latter was phosphorylated at its two C-terminal sites. We propose that this regulatory mechanism assists in the activation of phosphorylated AtPIP2;1 during circadian regulation of K_ros.

Cultivated peanut (Arachis hypogaea L.) is an important oil crop for human nutrition and is cultivated in >100 countries. However, the present knowledge of its genomic diversity, evolution, and loci related to the seed traits is limited. Our study intended to (1) uncover the population structure and the demographic history of peanuts, (2) identify signatures of selection that occurred during peanut improvement breeding, and (3) detect and verify the functions of candidate genes associated with seed traits. We explored the population relationship and the evolution of peanuts using a largescale single nucleotide polymorphism dataset generated from the genome-wide resequencing of 203 cultivated peanuts. Genetic diversity and genomic scan analyses were applied to identify selective loci for genomic-selection breeding. Genome-wide association studies, transgenic experiments, and RNA-seq were employed to identify the candidate genes associated with seed traits. Our study revealed that the 203 resequenced accessions were divided into four genetic groups, consistent with their botanical classification. Moreover, the var. peruviana and var. fastigiata subpopulations have diverged to a greater extent than the others, and var. peruviana may be the earliest variant in the evolution from tetraploid ancestors. A recent dramatic expansion in the effective population size of the cultivated peanuts ca. 300–500 years ago was also noted. Selective sweeps underlying quantitative trait loci and genes of seed size, plant architecture, and disease resistance coincide with the major goals of improved peanut breeding compared with the landrace and cultivar populations. Genome-wide association testing with functional analysis led to the identification of two genes involved in seed weight and seed length regulation. Our study provides valuable information for understanding the genomic diversity and the evolution of peanuts and serves as a genomic basis for improving peanut cultivars.