Engineering homoeologs provide a fine scale for quantitative traits in polyploid

An Improved and Simplified Agrobacterium-Mediated Genetic Transformation Protocol for Solanum nigrum with a Shorter Growth Time

Solanum nigrum (Solanaceae family) is widely consumed as a fruit or local leafy vegetable after boiling; it also serves as a medicinal plant. Although Agrobacterium-mediated genetic transformation has been established in S. nigrum, the transformation period is long. Specifically, induction of roots takes approximately five weeks for tetraploid and hexaploid S. nigrum, and 7 weeks for diploid Solanum americanum. In this study, we developed an improved rooting-induced method that requires only about 1 week and avoids the use of tissue culture. After generating the transgenic shoots, they were directly transplanted into the soil to facilitate root formation. Remarkably, 100% of the transgenic shoots developed roots within 6 days. Our improved method is time-saving (saving more than 1 month) and simpler to operate. The improved rooting-induced step can be applied to induce roots in various plants using tissue culture, exemplified by the carnation (Dianthus caryophyllus L.). Furthermore, we applied the improved method to generate S. americanum plants expressing AcMYB110 from kiwifruit (Actinidia chinensis spp.). This method will contribute to speeding up gene functional analysis and trait improvement in S. nigrum and might have potential in fast plant molecular breeding processes in crops and rapid rooting induction in tissue culture.

Optimization of CRISPR-Cas9 system in Eustoma grandiflorum

The optimization of the CRISPR-Cas9 system for enhancing editing efficiency holds significant value in scientific research. In this study, we optimized single guide RNA and Cas9 promoters of the CRISPR-Cas9 vector and established an efficient protoplast isolation and transient transformation system in Eustoma grandiflorum, and we successfully applied the modified CRISPR-Cas9 system to detect editing efficiency of the EgPDS gene. The activity of the EgU6-2 promoter in E. grandiflorum protoplasts was approximately three times higher than that of the GmU6 promoter. This promoter, along with the EgUBQ10 promoter, was applied in the CRISPR-Cas9 cassette, the modified CRISPR-Cas9 vectors that pEgU6-2::sgRNA-2/pEgUBQ10::Cas9-2 editing efficiency was 37.7%, which was 30.3% higher than that of the control, and the types of mutation are base substitutions, small fragment deletions and insertions. Finally we obtained an efficient gene editing vector for E. grandiflorum. This project provides an important technical platform for the study of gene function in E. grandiflorum.

Genomic evidence for rediploidization and adaptive evolution following the whole-genome triplication

Whole-genome duplication (WGD), or polyploidy, events are widespread and significant in the evolutionary history of angiosperms. However, empirical evidence for rediploidization, the major process where polyploids give rise to diploid descendants, is still lacking at the genomic level. Here we present chromosome-scale genomes of the mangrove tree Sonneratia alba and the related inland plant Lagerstroemia speciosa. Their common ancestor has experienced a whole-genome triplication (WGT) approximately 64 million years ago coinciding with a period of dramatic global climate change. Sonneratia, adapting mangrove habitats, experienced extensive chromosome rearrangements post-WGT. We observe the WGT retentions display sequence and expression divergence, suggesting potential neo- and sub-functionalization. Strong selection acting on three-copy retentions indicates adaptive value in response to new environments. To elucidate the role of ploidy changes in genome evolution, we improve a model of the polyploidization-rediploidization process based on genomic evidence, contributing to the understanding of adaptive evolution during climate change.

Chromosome-scale assembly and gene editing of Solanum americanum genome reveals the basis for thermotolerance and fruit anthocyanin composition

Solanum americanum serves as a promising source of resistance genes against potato late blight and is considered as a leafy vegetable for complementary food and nutrition. The limited availability of high-quality genome assemblies and gene annotations has hindered the exploration and exploitation of stress-resistance genes in S. americanum. Here, we present a chromosome-level genome assembly of a thermotolerant S. americanum ecotype and identify a crucial heat-inducible transcription factor gene, SaHSF17, essential for heat tolerance. The CRISPR/Cas9 system-mediated knockout of SaHSF17 results in remarkably reduced thermotolerance in S. americanum, exhibiting a significant suppression of multiple HSP gene expressions under heat treatment. Furthermore, our transcriptome analysis and anthocyanin component investigation of fruits indicated that delphinidins are the major anthocyanins accumulated in the mature dark-purple fruits. The accumulation of delphinidins and other pigment components during fruit ripening in S. americanum coincides with the transcriptional regulation of key genes, particularly the F3'5'H and F3'H genes, in the anthocyanin biosynthesis pathway. By integrating existing knowledge, the development of this high-quality reference genome for S. americanum will facilitate the identification and utilization of novel abiotic and biotic stress-resistance genes for improvement of Solanaceae and other crops.