Soil salinity is a growing concern for global crop production and the sustainable development of humanity. Therefore, it is crucial to comprehend salt tolerance mechanisms and identify salt-tolerance genes to enhance crop tolerance to salt stress. Suaeda glauca, a halophyte species well adapted to the seawater environment, possesses a unique ability to absorb and retain high salt concentrations within its cells, particularly in its leaves, suggesting the presence of a distinct mechanism for salt tolerance. In this study, we performed de novo sequencing of the S. glauca genome. The genome has a size of 1.02 Gb (consisting of two sets of haplotypes) and contains 54 761 annotated genes, including alleles and repeats. Comparative genomic analysis revealed a strong synteny between the genomes of S. glauca and Beta vulgaris. Of the S. glauca genome, 70.56% comprises repeat sequences, with retroelements being the most abundant. Leveraging the allele-aware assembly of the S. glauca genome, we investigated genome-wide allele-specific expression in the analyzed samples. The results indicated that the diversity in promoter sequences might contribute to consistent allele-specific expression. Moreover, a systematic analysis of the ABCE gene families shed light on the formation of S. glauca’s flower morphology, suggesting that dysfunction of A-class genes is responsible for the absence of petals in S. glauca. Gene family expansion analysis demonstrated significant enrichment of Gene Ontology (GO) terms associated with DNA repair, chromosome stability, DNA demethylation, cation binding, and red/far-red light signaling pathways in the co-expanded gene families of S. glauca and S. aralocaspica, in comparison with glycophytic species within the chenopodium family. Time-course transcriptome analysis under salt treatments revealed detailed responses of S. glauca to salt tolerance, and the enrichment of the transition-upregulated genes in the leaves associated with DNA repair and chromosome stability, lipid biosynthetic process, and isoprenoid metabolic process. Additionally, genome-wide analysis of transcription factors indicated a significant expansion of FAR1 gene family. However, further investigation is needed to determine the exact role of the FAR1 gene family in salt tolerance in S. glauca.

JASMONATE ZIM-DOMAIN (JAZ) proteins are negative regulators of the jasmonate (JA)-signaling pathway and play pivotal roles in plant resistance to biotic and abiotic stresses. Genome-wide identification of JAZ genes has been performed in many plant species. However, systematic information about pineapple (Ananas comosus L. Merr.) JAZ genes (AcJAZs) is still not available. In this study, we identified 14 AcJAZ genes and classified them into five groups along with the Arabidopsis and rice orthologs. The AcJAZ genes have 3–10 exons, and the putative AcJAZ proteins have between two and eight conserved regions, including the TIFY motif and Jas domain. The cis-acting element analysis revealed that the putative promoter regions of AcJAZs contain between three and eight abiotic stress-responsive cis-acting elements. The gene-expression analysis suggested that AcJAZs were expressed differentially during plant development and subjected to regulation by the cold, heat, salt, and osmotic stresses as well as by phytohormones. Moreover, the BiFC analysis of protein interactions among the central JA-signaling regulators showed that AcJAZ4, AcMYC2, AcNINJA, and AcJAM1 could interact with AcJAZ5 and AcJAZ13 in vivo, indicating a canonical JA-signaling pathway in pineapple. These results increase our understanding of the functions of AcJAZs and the responses of the core players in the JA-signaling pathway to abiotic stresses.

The ubiquitin-conjugating enzyme (E2) is required for protein ubiquitination. Arabidopsis has 37 E2s grouped into 14 subfamilies and the functions for many of them are unknown. We utilized genetic and biochemical methods to study the roles of Arabidopsis UBC4, UBC5, and UBC6 of the E2 subfamily IV. The Arabidopsis ubc4/5/6 triple mutant plants had higher levels of glucose, sucrose, and starch than the control plants, as well as a higher protein level of a key gluconeogenic enzyme, cytosolic fructose 1,6-bisphosphatase 1 (cyFBP). In an in vitro assay, the proteasome inhibitor MG132 inhibited the degradation of recombinant cyFBP whereas ATP promoted cyFBP degradation. In the quadruple mutant ubc4/5/6 cyfbp, the sugar levels returned to normal, suggesting that the increased sugar levels in the ubc4/5/6 mutant were due to an increased cyFBPase level. In addition, the ubc4/5/6 mutant plants showed early leaf senescence at late stages of plant development as well as accelerated leaf senescence using detached leaves. Further, the leaf senescence phenotype remained in the quadruple ubc4/5/6 cyfbp mutant. Our results suggest that UBC4/5/6 have two lines of important functions, in sugar metabolism through regulating the cyFBP protein level and in leaf senescence likely through a cyFBP-independent mechanism.

Protein ubiquitination is important for the regulation of meiosis in eukaryotes, including plants. However, little is known about the involvement of E2 ubiquitin-conjugating enzymes in plant meiosis. Arabidopsis UBC22 is a unique E2 enzyme, able to catalyze the formation of ubiquitin dimers through lysine 11 (K11). Previous work has shown that ubc22 mutants are defective in megasporogenesis, with most ovules having no or abnormally functioning megaspores; furthermore, some mutant plants show distinct phenotypes in vegetative growth. In this study, we showed that chromosome segregation and callose deposition were abnormal in mutant female meiosis while male meiosis was not affected. The meiotic recombinase DMC1, required for homologous chromosome recombination, showed a dispersed distribution in mutant female meiocytes compared to the presence of strong foci in WT female meiocytes. Based on an analysis of F1 plants produced from crosses using a mutant as the female parent, about 24% of female mutant gametes had an abnormal content of DNA, resulting in frequent aneuploids among the mutant plants. These results show that UBC22 is critical for normal chromosome segregation in female meiosis but not for male meiosis, and they provide important leads for studying the role of UBC22 and K11-linked ubiquitination.

The authors would like to make the following correction to the published paper