Plant Biotechnology Journal最新文献

The main genetic diversity observed in cultivated citrus results from a reticulate evolution involving four ancestral taxa whose radiation occurred in allopatry. In such context, GWAS analysis, genome diversity and transcriptomic studies will be significantly enhanced through pangenome approaches. We report the implementation of a super-pangenome for cultivated citrus, established with de novo assemblies of C. medica, C. reticulata and C. micrantha, released for the first time alongside a published chromosome-scale assembly of C. maxima. Repetitive element annotation revealed that half of each genome consisted of transposable elements or DNA-satellites. The new genome assemblies display strong synteny and collinearity, while discrepancies are observed with the C. maxima assembly. Resequencing information from 55 accessions helped to explore the intra- and interspecific diversity of the ancestral taxa and their relationships with horticultural groups. Diagnostic SNPs of the ancestral taxa revealed interspecific introgressions in several representative accessions of C. reticulata, C. maxima and C. medica as well as insights into the origin and phylogenomic structures of horticultural groups. PAV analysis revealed a gene whose absence or presence was specific to one of the ancestral taxa. Diagnostic PAV analysis uncovered a large chloroplastic introgression in C. medica chromosome 4. The analysis of the functional enrichment and species-specific adaptations in the citrus super-pangenome revealed distinct functional specialisations. This highlights the evolutionary paths that have shaped species, contributing to the diversity in the citrus super-pangenome while maintaining a shared foundation of essential biological processes. We established a Genome Hub, offering a platform for continuous genomic research.

The escalating global temperatures and intensifying heat stress events pose significant threats to maize productivity worldwide. Uncovering key thermotolerance genes and their functional mechanisms is thus critical for developing climate-resilient crops. Here, we report that ZmCTU2, a cytoplasmic tRNA thiolation factor, acts as a central regulator of heat tolerance in maize. Expression of ZmCTU2 correlates positively with kernel-setting under high temperatures. Overexpression of ZmCTU2 confers enhanced thermotolerance at both seedling and adult stages, improving survival and field yield under heat stress, whereas loss-of-function mutants of ZmCTU2 or its partner ZmCTU1 display severe seed developmental defects and lethality. Mechanistically, ZmCTU2 translocates to stress granules under thermal stress, where it recruits ZmCTU1 and ROS-scavenging peroxidases, shielding them from degradation. This dual recruitment facilitates synergistic protective responses: maintenance of tRNA thiolation to ensure translational fidelity, and stabilisation of antioxidative enzymes to bolster redox homeostasis. Our study identifies ZmCTU2 as a scaffold protein within stress granules that coordinates proteostatic and antioxidative pathways under heat stress, providing a valuable genetic resource for engineering thermotolerant maize.

Vitamin A deficiency (VAD), a major global health concern, has driven efforts to develop staple crops with enhanced pro-vitamin A (pVA) content. Delivering meaningful nutritional benefits, however, requires technologies that maintain elevated carotenoid levels under field conditions. Previous proof-of-concept work demonstrated that pVA content can be substantially increased in Cavendish bananas through genetic modification, providing a platform for transferring the technology into East African Highland banana (EAHB) cultivars relevant to reducing VAD in Uganda. To evaluate performance under agronomic conditions, we conducted multi-generational field assessments of 27 transgenic Cavendish lines generated from seven constructs enabling constitutive or fruit-preferred expression of three carotenoid biosynthesis genes: ZmPsy1, MtPsy2a and PaCrtI. Constitutive expression was driven by the maize Ubi promoter, while fruit expression was regulated by Exp1 or ACO promoters. Agronomic performance and fruit carotenoid levels were analysed across three generations to explore factors influencing pVA enhancement. All transgenic lines exhibited increased fruit pVA, with the highest accumulation observed in lines constitutively expressing MtPsy2a. Promoter-transgene combinations significantly affected carotenoid accumulation and the stability of the trait in the field. PVA accumulation was the highest in the initial sucker crop and declined in subsequent ratoons, reflecting sensitivity to seasonal conditions. While ACO- and Ubi-driven lines were less affected by seasonal temperature changes, these variations significantly constrained pVA accumulation in wild-type and Exp1-regulated lines. This comprehensive assessment helps elucidate the complex interplay of promoter, isoform, and environmental factors that are essential for the long-term viability of nutritional interventions aimed at combating VAD in the region.