Self-incompatibility (SI) is a complex mechanism that prevents plants from self-fertilizing to preserve and promote genetic variability. The angiosperm species have developed two different SI systems, the sporophytic (SSI) and the gametophytic (GSI) systems. SI is a significant impediment to steady fruit production in fruit tree species of the Rosaceae. In Rosaceae, GSI is genetically regulated via a single locus, named the ‘S-locus’, which includes a minimum of two polymorphic and relatively intercorrelated S genes: a pistil-expressed S-RNase gene and several pollen-expressed SFBB (S-locus F-Box Brothers) or SFB (S haplotype-specific F-box protein). This necessitates the interaction of S-RNases with the male determinants. Although genetic and molecular analyses of S genes have shown that mutations in both pistils and pollen-specific components induce self-compatibility in many species and cultivars, other genes or molecules outside the S-locus can co-participate in the male gamete rejection in GSI. However, we highlight and synthesize the most recent knowledge on different mechanisms of GSI in Rosaceae in this current review.

Prunus zhengheensis, an extremely rare population of apricots, originated in warm South-East China and is an excellent material for genetic breeding. However, most apricots and two related species (P. sibirica, P. mandshurica) are found in the cold northern regions in China and the mechanism of their distribution is still unclear. In addition, the classification status of P. zhengheensis is controversial. Thus, we generated a high-quality haplotype-resolved genome for P. zhengheensis, exploring key genetic variations in its adaptation and the causes of phylogenetic incongruence. We found extensive phylogenetic discordances between the nuclear and organelle phylogenies of P. zhengheensis, which could be explained by incomplete lineage sorting. A 242.22-Mb pan-genome of the Armeniaca section was developed with 13 chromosomal genomes. Importantly, we identified a 566-bp insertion in the promoter of the HSFA1d gene in apricot and showed that the activity of the HSFA1d promoter increased under low temperatures. In addition, HSFA1d overexpression in Arabidopsis thaliana indicated that HSFA1d positively regulated plant growth under chilling. Therefore, we hypothesized that the insertion in the promoter of HSFA1d in apricot improved its low-temperature adaptation, allowing it to thrive in relatively cold locations. The findings help explain the weather adaptability of Armeniaca plants.

The formation of multi-pistil flowers reduces the yield and quality in Japanese apricot (Prunus mume). However, the molecular mechanism underlying the formation of multi-pistil flowers remains unknown. In the current study, overexpression of PmKNAT2/6-a, a class I KNOTTED1-like homeobox (KNOX) member, in Arabidopsis (Arabidopsis thaliana) resulted in a multi-pistil phenotype. Analysis of the upstream regulators of PmKNAT2/6-a showed that AGAMOUS-like 24 (PmAGL24) could directly bind to the PmKNAT2/6-a promoter and regulate its expression. PmAGL24 also interacted with Like Heterochromatin Protein 1 (PmLHP1) to recruit lysine trimethylation at position 27 on histone H3 (H3K27me3) to regulate PmKNAT2/6-a expression, which is indirectly involved in multiple pistils formation in Japanese apricot flowers. Our study reveals that the PmAGL24 transcription factor, an upstream regulator of PmKNAT2/6-a, regulates PmKNAT2/6-a expression via direct and indirect pathways and is involved in the formation of multiple pistils in Japanese apricot.

Japanese apricot (Prunus mume Sieb. et Zucc.) is a dicotyledonous plant from the Rosaceae family that originated in China. Functional genomic studies in Japanese apricot are essential to elucidate the molecular mechanisms underlying key agronomic traits and to accelerate crop improvement. However, the lack of an efficient genetic transformation system has hindered gene function analysis and impeded molecular breeding efforts. Agrobacterium rhizogenes-mediated transformation has emerged as a robust tool for functional gene validation and studying root-specific processes across diverse plant species, due to its simple protocol and rapid turnaround time. Notably, Agrobacterium-mediated transformation remains notoriously recalcitrant in Rosaceae species, particularly in Japanese apricot. Through screening of ten Japanese apricot varieties, we identified ‘Muguamei’ (MGM) as the optimal cultivar for tissue culture. Using its genotype, we established an Agrobacterium rhizogenes-mediated transformation system for Japanese apricot via an in vitro approach. The binary vector incorporated the RUBY reporter for visual selection and eYGFPuv for fluorescent validation of transformation events. Furthermore, CRISPR/Cas9-mediated knockout of PmPDS in ‘Muguamei’ calli generated albino phenotypes, confirming successful genome editing. Through optimization of antibiotics, the study achieved an 80% explant survival rate using Woody Plant Medium (WPM) supplemented with 6-BA (0.5 mg/L) and TDZ (0.05 mg/L). For in vitro micropropagation, we found that ‘Muguamei’ exhibited optimal shoot growth in the presence of 6-BA (0.06 mg/L) and TDZ (0.1 mg/L), and up to 8 bud proliferation lines could be reached under 4.0 mg/L 6-BA. During the rooting of micro shoots, ½MS medium performed better and reached the optimum root length (35.70 ± 4.56 mm) and number (6.00 ± 1.00) under IAA (0.5 mg/L) and IBA (0.4 mg/L). Leaf explants were cultured on WPM supplemented with TDZ (4.0 mg/L) and NAA (0.2 mg/L). 50 mg/L kanamycin concentrations were the suitable screening concentration.

Potassium (K⁺) is a vital macronutrient for plant growth and stress resilience, with KT/HAK/KUP transporters playing a central role in its homeostasis. Although these transporters are known to influence photosynthesis, the molecular mechanisms by which fertilization promotes assimilate accumulation in peach crops remain poorly understood. In this study, 17 PpHAK genes were identified based on the peach genome and classified into four distinct clades through phylogenetic analysis, a classification further supported by conserved gene structures and motifs. Interspecific collinearity analysis revealed that transporters are highly conserved among Rosaceae species. Physiological measurements demonstrated that foliar application significantly enhanced photosynthetic capacity, as evidenced by a 33% increase in net photosynthetic rate (Pn) and improved photoelectron yield (Y(II)). At the same time, the transcript levels of the transporters PpHAK1, PpHAK5, and PpHAK9 were significantly upregulated, as confirmed by quantitative real-time RT-PCR (qRT-PCR) analysis. Furthermore, the expression of genes involved in sugar metabolism and transport, particularly PpPLT5-1, was significantly induced. Collectively, these results indicate that foliar K⁺ application enhances photosynthesis and promotes assimilate accumulation by modulating the expression of both K⁺ and sugar transporters. These findings offer a theoretical basis for optimizing nutrient management to improve fruit quality in stone fruit production.