Ping Zheng

Self-incompatibility (SI) is an important plant mechanism that prevents inbreeding depression by recognizing and rejecting self-pollen, thereby promoting outcrossing. However, SI can also act as a barrier in breeding programs, presenting significant challenges to breeders. Passion fruit (Passiflora edulis), a tropical fruit species of substantial economic importance, also serves as a valuable system for investigating SI mechanisms within the Passifloraceae. Nevertheless, the molecular basis of SI in passion fruit has not yet been elucidated. In this study, we investigated the SI system in yellow passion fruit (P. edulis f. flavicarpa) and employed transcriptomic analysis to examine the time-course transcriptional responses following different pollination treatments. Transcriptomic analysis revealed distinct gene expression dynamics under different pollination treatments: self-pollinated samples exhibited stronger and earlier transcriptional changes, whereas the number of differentially expressed genes (DEGs) in cross-pollinated samples was relatively lower. Numerous pathways previously associated with sporophytic self-incompatibility (SSI) were enriched in the stigma samples after self-pollination. Reactive oxygen species (ROS) are crucial signaling molecules involved in pollen germination and pollen tube growth during SI responses. Our results showed that ROS-related pathways were enriched in stigma tissues after self-pollination. In addition, oxidative stress-related responses were detected in the style shortly after self-pollination, suggesting that plastid-associated or general oxidative stress processes may also be involved, although the precise source of ROS requires further validation. FERONIA, ROP9, and ARC1 are key genes related to the SI system in Brassica. In the passion fruit SI response, the expression levels of these genes increased in the style, indicating a spatial expression pattern different from that reported in classical Brassicaceae SSI systems. Together with cytological observations showing that self-pollen rejection occurs at the stigma surface, our results suggest that yellow passion fruit may employ an SSI-like regulatory framework while exhibiting a lineage-specific spatial deployment of SI-related regulators. Overall, this study provides new transcriptomic insights into the SI mechanism of yellow passion fruit, establishes a molecular framework for understanding SI in P. edulis f. flavicarpa, and offers novel insights into the diversity of plant SI systems.

This study presented the complete mitogenome of the cubozoan Morbakka virulenta Kishinouyea, 1910, assembled into eight linear chromosomes (ranging 702–3790 bp) and encoding 13 protein-coding genes (PCGs), two rRNAs (rns and rnl), and one tRNA (trnM). Phylogenomic analyses robustly supported M. virulenta and Morbakka sp. as monophyletic sister species, forming a clade sister to Carukia barnesi. The genus-specific localization of rns and nad4 indicated dynamic mitogenome reorganization in cubozoans. However, the gene order of 13 PCGs was conserved in M. virulenta, Morbakka sp., Alatina alata, and Alatina moseri, as in Staurozoa and Scyphozoa, revealing a shared ancestral architecture for Medusozoa.

Clinacanthus nutans is a traditional medicinal plant widely used in Southeast Asia for treating inflammation, viral infections, and cancer. However, its molecular basis remains poorly understood. In this study, the first chromosome-scale genome of C. nutans (731.61 Mbp) was assembled, with 93.76% anchored to 18 pseudochromosomes. Repetitive elements constituted 69.05% of the genome, predominantly long terminal repeat retrotransposons. Phylogenomic and synonymous substitution rate analyses revealed a Lamiales-wide whole-genome duplication event, followed by extensive chromosomal rearrangements. Gene family expansion analysis showed that segmental and dispersed duplications were the primary drivers of enzyme-coding genes (EGs) expansion involved in the flavonoid and triterpenoid pathways. Integrated transcriptomic and metabolomic analyses across five organs revealed distinct organ-specific expression and metabolite profiles. Genes exhibited pronounced differential expression between leaves and roots, with enrichment in flavonoid and triterpenoid biosynthetic pathways, highlighting functional divergence and metabolic specialization. Flavonoids were enriched in aerial tissues, whereas triterpenoids accumulated in roots. Weighted gene co-expression network analysis identified key EGs (e.g. CHS, CHI, OSC) and core transcription factors (e.g. MYB, bHLH, WRKY) potentially involved in organ-specific metabolic regulation. These findings suggest a coordinated transcriptional-metabolic regulatory framework underlying the specialized functions of different tissues. This work provides valuable genomic resources and mechanistic insights into the biosynthesis and regulation of bioactive compounds in C. nutans, thereby facilitating future research and molecular breeding of this important ethnomedicinal plant.

Oenothera species are increasingly valued for their medicinal and ornamental qualities and serve as important models in classical cytoplasmic genetics research. The genus Oenothera L., one of the largest in the Onagraceae family, includes 18 subsections and two deep phylogenetic lineages, Clade A and Clade B. Analyzing high-quality chloroplast genomes can provide crucial insights into species classification and genus-level evolution. In this study, we report the complete chloroplast genome of Oenothera drummondii Hook., the first species from subsection Raimannia, with a total length of 167,177 bp and a GC content of 39.3%. This genome contains 129 genes and displays a typical quadripartite structure. Combining this genome with data from 16 publicly available chloroplast genomes, we conducted a comprehensive comparative and evolutionary analysis. Our results indicate that Clade B species diverged independently from Clade A species. Within Clade A, species from subsection Muniza form a distinct branch, while O. drummondii clusters closely with species from subsection Oenothera. Phylogenetic analysis correlates well with chloroplast genome structural differences, such as the loss of the infA gene in Clade B species, the expansion of the IR regions in Muniza, and a shared large inversion in the LSC region among Raimannia and Oenothera species. We also identified repeat sequences, six highly variable genes, and positively selected genes among the 17 chloroplast genomes analyzed. These findings offer valuable insights into the evolutionary processes of Oenothera species and provide a foundation for the development of future molecular markers based on the identified genes and structural variations. Graphical Abstract

The WUSCHEL-related homeobox (WOX) transcription factors (TF) regulate critical developmental processes in plants, including organ formation and stem cell maintenance. Although characterized in model species, the WOX family remains unexplored in passion fruit (Passiflora edulis). In this study, 10 WOX genes were identified in passion fruit, which are distributed across six chromosomes. We analyzed the phylogenetic relationships, gene structure, conserved motifs, and syntenic relationships of the PeWOX genes. Multiple sequence alignment analysis revealed strong conservation of the homeodomain region among WOX TF family members. Phylogenetic reconstruction further demonstrated that the 10 identified PeWOX genes in passion fruit could be classified into three distinct evolutionary clades: the WUS clade, the Intermediate clade, and the Ancient clade. The conserved motif and gene structure of WOX TF family members in the same evolutionary clade were highly consistent. Expression analysis based on RNA-seq and RT-qPCR showed that most PeWOX genes were expressed during ovule development. The expression level of PeWOX genes varies with different stress conditions. Subcellular localization analysis of tobacco leaf epidermal cells showed that PeWOX3/7/10 proteins were localized in the nucleus and cell membrane. Collectively, this study lays a foundation for future functional studies of passion fruit WOX genes.

Late Embryogenesis Abundant (LEA) proteins play vital roles in plant responses to abiotic stress and developmental regulation. Pineapple (Ananas comosus L.) is a major tropical fruit crop with high economic value, but its production is often threatened by cold stress, particularly in regions at the northern margin of its cultivation. Despite the recognized importance of LEA proteins in stress adaptation, their genomic landscape and functional characteristics in pineapple remain largely unexplored. In this study, 37 AcLEA genes were identified in the pineapple (Ananas comosus L.) genome and classified into six subfamilies, with LEA_2 being the largest. Most AcLEA proteins were predicted to be hydrophilic, thermally stable, and intrinsically disordered, consistent with typical LEA protein characteristics. Phylogenetic and collinearity analyses revealed species-specific expansion patterns, primarily driven by segmental duplication events. Most duplicated gene pairs shared similar exon–intron structures, motif compositions, and expression profiles, although several displayed signs of functional divergence based on distinct expression patterns, Ka/Ks ratios > 1, and motif differences. Promoter cis-element, transcription factor, and miRNA network predictions indicated that AcLEA genes are widely involved in stress responses as well as growth and development. Expression profiling showed that many AcLEA genes including AcLEA32, AcLEA7, AcLEA9, AcLEA30, AcLEA29, AcLEA33, and AcLEA18 were significantly upregulated under cold stress and declined upon stress removal, indicating a potential role in cold tolerance. Some AcLEA genes, such as AcLEA32 and AcLEA33, showed faster and stronger induction under cold stress in the cold-tolerant cultivar “Comte de Paris” (BL) compared to the sensitive cultivar “Tainong No. 20” (NN), suggesting that differential gene responsiveness may contribute to cultivar-specific cold tolerance. Additionally, most AcLEA genes exhibited distinct spatiotemporal expression patterns across floral organs and fruit at various developmental stages, suggesting their involvement in reproductive development. These findings provide a foundation for future functional studies and highlight candidate genes for improving cold resilience and developmental traits in pineapple through molecular breeding.

Pineapple (Ananas comosus L.), an economically significant tropical fruit crop, is highly susceptible to low-temperature during cultivation. The abscisic acid (ABA) and stress-inducible HVA22 gene family is known to play important roles in growth regulation and abiotic stress response, but its functions in pineapple remain unclear. We identified 11 HVA22 genes (AcHVA22A - AcHVA22K) in the pineapple genome and grouped them into four phylogenetic clades. Expression analysis showed that most AcHVA22 genes displayed tissue- or developmental stage-specific expression patterns, suggesting their diverse functions in pineapple growth and development. Subcellular localization analyses revealed diverse localizations of AcHVA22 proteins, including plasma membrane, cytoplasm, and nucleus. And regulatory predictions indicated control by multiple cis-elements, transcription factors, and miRNAs, which may contribute to their functional diversification. Most AcHVA22 genes responded consistently to ABA, GA, and drought treatments, but their responses to high and low-temperatures varied. Notably, AcHVA22C/D/E/G/I/K were up-regulated under both short- and long-term cold treatments in two different pineapple varieties, highlighting their potential key roles in cold stress tolerance. This study provided the first genome-wide characterization of the HVA22 gene family in pineapple. The identification of candidate genes involved in cold stress response offers new insights into HVA22 functions in tropical fruits and provides valuable resources for improving cold resistance in pineapple breeding.

This study presents the first mitochondrial genome (16,342 bp) of the invasive species Cladonema digitatum Fang et al., 2022, revealing a conserved Capitata-like gene arrangement, comprising 13 protein-coding genes, two rRNA genes, and two tRNA genes, along with a duplicated pseudo-cox1 fragment. Phylogenetic analysis robustly supported C. digitatum and Cladonema multiramosum as reciprocally monophyletic mitogenome lineages, forming a robust clade sister to Cladonema pacificum. This topology supports the morphological dichotomy between the Cladonema radiatum-like lineage (filiform tentacles, gastric pouches) and C. pacificum-like species. These findings contribute a critical genomic resource for advancing the understanding of medusozoan phylogeny.

Understanding the metabolic characteristics of pineapple varieties is crucial for market expansion and diversity. This study performed comparative metabolomic analysis on the “Comte de Paris” (BL) and three Taiwan-introduced varieties: “Tainong No. 11” (XS), “Tainong No. 23” (MG), and “Tainong No. 13” (DM). A total of 551 metabolites were identified across the four varieties, with 231 metabolites exhibiting no significant differences between all varieties. This included major sugars such as sucrose, glucose, and fructose, as well as key acids like citric, malic, and quinic acids, indicating that the in-season maturing fruits of different pineapple varieties can all achieve good sugar–acid accumulation under suitable conditions. The differentially accumulated metabolites (DAMs) that were identified among the four varieties all primarily belonged to several major subclasses, including phenolic acids, flavonoids, amino acids and derivatives, and alkaloids, but the preferentially accumulated metabolites in each variety varied greatly. Specifically, branched-chain amino acids (L-leucine, L-isoleucine, and L-valine) and many DAMs in the flavonoid, phenolic acid, lignan, and coumarin categories were most abundant in MG, which might contribute to its distinct and enriched flavor and nutritional value. XS, meanwhile, exhibited a notable accumulation of aromatic amino acids (L-phenylalanine, L-tryptophan), various phenolic acids, and many lignans and coumarins, which may be related to its unique flavor profile. In DM, the dominant accumulation of jasmonic acid might contribute to its greater adaptability to low temperatures during autumn and winter, allowing off-season fruits to maintain good quality. The main cultivar BL exhibited the highest accumulation of L-ascorbic acid and many relatively abundant flavonoids, making it a good choice for antioxidant benefits. These findings offer valuable insights for promoting different varieties and advancing metabolome-based pineapple improvement programs.