Crossover hotspots are strikingly distinct among rice subspecies, despite their relatively recent divergence, and associate with DNA transposons and distinct pa

Potato (Solanum tuberosum) is the third most important food crop in the world. Potato tubers must be stored at cold temperatures to minimize sprouting and losses due to disease. However, cold temperatures strongly induce the expression of the potato vacuolar invertase gene (VInv) and cause reducing sugar accumulation. This process, referred to as “cold-induced sweetening,” is a major postharvest problem for the potato industry. We discovered that the cold-induced expression of VInv is controlled by a 200 bp enhancer, VInvIn2En, located in its second intron. We identified several DNA motifs in VInvIn2En that bind transcription factors involved in the plant cold stress response. Mutation of these DNA motifs abolished VInvIn2En function as a transcriptional enhancer. We developed VInvIn2En deletion lines in both diploid and tetraploid potato using clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated nuclease 9 (Cas9)-mediated gene editing. VInv transcription in cold-stored tubers was significantly reduced in the deletion lines. Interestingly, the VInvIn2En sequence is highly conserved among distantly related Solanum species, including tomato (Solanum lycopersicum) and other non-tuber-bearing species. We conclude that the VInv gene and the VInvIn2En enhancer have adopted distinct roles in the cold stress response in tubers of tuber-bearing Solanum species.

Polyploid plants typically display advantages on some agronomically important traits over their diploid counterparts. Extensive studies have shown genetic, transcriptomic, and epigenetic dynamics upon polyploidization in multiple plant species. However, few studies have unveiled those alternations imposed only by ploidy level, without any interference from heterozygosity. Cultivated potato is highly heterozygous. Thus, in this study, we developed two homozygous autotetraploid lines and one homozygous diploid line in parallel from a homozygous diploid potato. We confirmed their ploidy levels using chloroplast counting and karyotyping. Oligo-FISH and genome re-sequencing validated that these potato lines are nearly homozygous. We investigated variations in phenotypes, transcription, and histone modifications between two ploidies. Both autotetraploid lines produced larger but fewer tubers than the diploid line. Interestingly, each autotetraploid line displayed ploidy-related differential expression for various genes. We also discovered a genome-wide enrichment of H3K27ac in genic regions upon whole-genome doubling (WGD). However, such enrichment was not associated with the differential gene expression between two ploidies. The tetraploid lines may exhibit better resistance to cold-induced sweetening (CIS) than the diploid line in tubers, potentially regulated through the expression of CIS-related key genes, which seems to be associated with the levels of H3K4me3 in cold-stored tubers. These findings will help to understand the impacts of autotetraploidization on dynamics of phenotypes, transcription, and histone modifications, as well as on CIS-related genes in response to cold storage.

The pathogen Verticillium dahliae secreted effector V. dahliae Aspf2-like protein (VDAL) has been found to cause leaf wilting in cotton, but the ectopic expression of VDAL-encoding gene enhances the resistance to V. dahliae in cotton and Arabidopsis. The application of the VDAL protein powder with optimal dosage promotes the growth and yield in multiple crop species, such as rice and wheat. However, the promotive effects of VDAL on these aspects are sporadically reported in asexually propagated species, including potato, while the molecular regulatory network involved in the process remains unclear. In this study, we observed that VDAL promotes sprouting of the potato pre-basic seed (PBS) tubers and enhances the development of both above-ground and below-ground tissues. Strikingly, VDAL increases the tuber yield in both greenhouse and field trials by up to 18.97%. The time-course transcriptomic analysis and the endogenous phytohormone detection revealed that cytokinin may play an important role in response to VDAL-promoted growth. Interestingly, VDAL-treated PBS tubers show higher resistance to cold temperature (late-spring cold), a phenomenon that is diminished when the lovastatin, a cytokinin inhibitor is applied, indicating that the VDAL-promoted potato growth, particularly under low temperature, is associated with cytokinin.

Crop breeding requires a balance of tradeoffs among key agronomic traits caused by gene pleiotropy. The molecular manipulation of genes can effectively improve target traits, but this may not reduce gene pleiotropy, potentially leading to undesirable traits or even lethal conditions. However, molecular editing of cis-regulatory elements (CREs) of target genes may facilitate the dissection of gene pleiotropy to fine-tune gene expression. In this study, we developed a pipeline, in potato, which employs open chromatin to predict candidate CREs, along with both transient and genetic assays to validate the function of CREs and CRISPR/Cas9 to edit candidate CREs. We used StCDF1 as an example, a key gene for potato tuberization and identified a 288 bp-core promoter region, which showed photoperiodic inducibility. A homozygous CRISPR/Cas9-editing line was established, with two deletions in the core promoter, which displayed a reduced expression level, resulting in late tuberization under both long-day and short-day conditions. This pipeline provides an alternative pathway to improve a specific trait with limited downside on other phenotypes.