Kiwifruit (Actinidia chinensis Planch.) is a functionally dioecious plant, which displays diverse morphology in male and female flowers. MADS-box is an ancient and huge gene family that plays a key role in plant floral organ differentiation. In this study, we have identified 89 MADS-box genes from A. chinensis Red 5 genome. These genes are distributed on 26 chromosomes and are classified into type I (21 genes) and type II (68 genes). Overall, type II AcMADS-box genes have more complex structures than type I with more exons, protein domains, and motifs, indicating that type II genes may have more diverse functions. Gene duplication analysis showed that most collinearity occurred in type II AcMADS-box genes, which was consistent with a large number of type II genes. Analysis of cis-acting elements in promoters showed that AcMADS-box genes are mainly associated with light and phytohormone responsiveness. The expression profile of AcMADS-box genes in different tissues showed that most genes were highly expressed in flowers. Further, the qRT-PCR analysis of the floral organ ABCDE model-related genes in male and female flowers revealed that AcMADS4, AcMADS56, and AcMADS70 were significantly expressed in female flowers. It indicated that those genes may play an important role in the sex differentiation of kiwifruit. This work provided a comprehensive analysis of the AcMADS-box genes and may help facilitate our understanding of the sex differentiation regulatory mechanism in kiwifruit.

Actinidia latifolia, with the highest vitamin C content in its genus, is a unique wild relative of kiwifruit that could be important for genetic breeding research. Climate change significantly influences the distribution range of wild plants. Accurately assessing the potential distribution of wild kiwifruit and its response to climate change is crucial for the effective protection and sustainable utilization of its germplasm resources. In this study, we utilized the optimized MaxEnt model to predict the potential habitats of A. latifolia in China, employing the jackknife test to assess the importance of environmental variables in our modeling process. The results showed that annual precipitation (Bio12) and temperature annual range (Bio7) emerged as the most influential environmental variables affecting the distribution of this kiwifruit wild relative. As radiative forcing and time increase, the potential habitats of A. latifolia in China are projected to shrink southward, thereby exacerbating habitat fragmentation. This research offers significant scientific references for the investigation, protection, cultivation, and application of wild relatives of the kiwifruit.

Soft rot, a devastating fungal disease, severely impacts kiwifruit during postharvest storage, causing substantial fruit damage and rendering the fruit inedible. Botryosphaeria dothidea (B. dothidea) is the primary pathogen causing kiwifruit soft rot, but its pathogenic mechanism remains unclear. In this study, morphological observation, transcriptome sequencing, and untargeted metabolomics were employed to analyze the changes in ‘Jinkui’ kiwifruit after artificial inoculation with B. dothidea. The results showed that obvious lesions began to appear on the fruit surface at 72 h post-inoculation (hpi) with B. dothidea, and the peel rot initiated at 120 hpi. Transcriptome sequencing revealed a significantly higher number of differentially expressed genes (DEGs) at 72 and 120 hpi than at 12 and 24 hpi. KEGG enrichment analysis indicated that DEGs at 72 and 120 hpi were significantly enriched in the plant hormone signal transduction pathway. A total of 403 metabolites were identified via untargeted metabolomics, among which the number of differentially accumulated metabolites (DAMs) was highest at 72 hpi (46 DAMs). These DAMs predominantly belong to the lipid and organic acid classes and are associated with pathways such as phenylpropanoid biosynthesis and secondary metabolite biosynthesis. Co-enrichment analysis revealed significant enrichment of DEGs and DAMs in the phenylpropanoid biosynthesis pathway. The correlation between DEGs and DAMs was assessed using the O2PLS model and the Pearson correlation coefficient. Two key DEGs were identified: a MYB transcription factor (Acc32263) and a ChlH-like gene (Acc00854), both of which potentially play crucial regulatory roles in the pathogenesis of kiwifruit soft rot. Significant changes in kiwifruit tissue morphology, gene expression, and metabolite profiles were observed after 72 h of B. dothidea infection. The plant hormone signal transduction and phenylpropanoid biosynthesis pathways are closely associated with the pathogenesis of kiwifruit soft rot. The MYB transcription factor (Acc32263) and the ChlH-like gene (Acc00854) are likely to be the key regulators. This study identifies the core regulatory pathways and genes involved in kiwifruit soft rot, provides new insights into the pathogenic mechanism of B. dothidea, and offers theoretical support for developing effective strategies to control kiwifruit soft rot.

The kiwifruit canker disease caused by Pseudomonas syringae pv. actinidiae (Psa) seriously threatens the development of kiwifruit industry. So far, only a limited number of Psa-resistant kiwifruit varieties have been identified, and the underlying molecular mechanisms are still largely unknown. In this study, we evaluated the Psa resistance of six hybrid populations and screened a resistant segregation population R₁F₂. Then, transcriptome analysis on the Psa extremely high-resistant (HR) and extremely high-susceptible (HS) plants of the R₁F₂ population was performed. KEGG enrichment analysis revealed that differentially expressed genes (DEGs) were significantly enriched in plant hormone signal transduction pathways, including auxin, abscisic acid, zeatin, jasmonic acid and salicylic acid. Furthermore, several transcription factors (TFs), especially WRKY TFs, were identified among the DEGs. The qRT-PCR showed that AcWRKY75 was highly expressed in the HS plants. Additionally, AcWRKY75 was significantly induced in the HS cultivar ‘Hongyang’ after Psa inoculation. Sequence amplification analysis showed that there was polymorphism in the DNA sequence of AcWRKY75 gene, but no HR or HS-specific differences were observed. Subcellular localization and transcriptional activity analysis confirmed that AcWRKY75 functions as a nucleus-located transcriptional activator. Transient overexpression of AcWRKY75 in kiwifruit leaves reduced the resistance to Psa, while silencing AcWRKY75 by virus-induced gene silencing (VIGS) slightly enhanced the resistance to Psa. Furthermore, AcWRKY75 exhibited a weak interaction with the promoter of the ABA-related DEG AcBet V1 (Acc27163). Our findings elucidated that AcWRKY75 may negatively regulate the Psa resistance of kiwifruit through the hormone signaling pathway, which laid a foundation for the analysis of the disease resistance mechanism of kiwifruit canker.

The genus Actinidia, which encompasses the widely cultivated kiwifruit, is characterized by its rich species diversity. Wild Actinidia species serve as invaluable germplasm reservoirs for crop improvement. As an important kiwifruit species, Actinidia hubeiensis represents a unique taxonomic group endemic to Hubei Province, contributing valuable genetic diversity to the genus Actinidia. Here, we present a haplotype-resolved genome assembly for A. hubeiensis. The two haplotype assemblies (Hap1 and Hap2) spanned 658.03 Mb (N50 = 23.16 Mb) and 597.19 Mb (N50 = 20.89 Mb), encoding 35,741 and 36,647 high-confidence protein-coding genes, respectively. Based on comprehensive assessments, both haplotypes demonstrated high completeness (BUSCO completeness > 99%), excellent continuity (LAI up to 21.67), low base-error rates (QV > 40), and nearly complete read mapping rates (> 98%). This genome assembly provides crucial genomic resources for the genus, enriching our understanding of kiwifruit biodiversity and offering new insights into the genetic background and evolutionary characteristics of this distinctive species.