The raffinose synthetase (RFS) and galactinol synthase (GolS) are two critical enzymes for raffinose biosynthesis, which play an important role in modulating plant growth and in response to a variety of biotic or abiotic stresses. Here, we comprehensively analyzed the RFS and GolS gene families and their involvement in abiotic and biotic stresses responses at the genome-wide scale in kiwifruit. A total of 22 GolS and 24 RFS genes were identified in Actinidia chinensis and Actinidia eriantha genomes. Phylogenetic analysis showed that the GolS and RFS genes were clustered into four and six groups, respectively. Transcriptomic analysis revealed that abiotic stresses strongly induced some crucial genes members including AcGolS1/2/4/8 and AcRFS2/4/8/11 and their expression levels were further confirmed by qRT-PCR. The GUS staining of AcRFS4Pro::GUS transgenic plants revealed that the transcriptionlevel of AcRFS4 was significantly increased by salt stress. Overexpression of AcRFS4 in Arabidopsis demonstrated that this gene enhanced the raffinose accumulation and the tolerance to salt stress. The co-expression networks analysis of hub transcription factors targeting key AcRFS4 genes indicated that there was a strong correlation between AcNAC30 and AcRFS4 expression under salt stress. Furthermore, the yeast one-hybrid assays showed that AcNAC30 could bind the AcRFS4 promoter directly. These results may provide insights into the evolutionary and functional mechanisms of GolS and RFS genes in kiwifruit.

Kiwifruit (Actinidia chinensis) is commonly covered by fruit hairs (trichomes) that affect kiwifruit popularity in the commercial market. However, it remains largely unknown which gene mediates trichome development in kiwifruit. In this study, we analyzed two kiwifruit species, A. eriantha (Ae) with long, straight, and bushy trichomes and A. latifolia (Al) with short, distorted, and spare trichomes, by second- and third-generation RNA sequencing. Transcriptomic analysis indicated that the expression of the NAP1 gene, a positive regulator of trichome development, was suppressed in Al compared with that in Ae. Additionally, the alternative splicing of AlNAP1 produced two short transcripts (AlNAP1-AS1 and AlNAP1-AS2) lacking multiple exons, in addition to a full-length transcript of AlNAP1-FL. The defects of trichome development (short and distorted trichome) in Arabidopsis nap1 mutant were rescued by AlNAP1-FL but not by AlNAP1-AS1. AlNAP1-FL gene does not affect trichome density in nap1 mutant. The qRT−PCR analysis indicated that the alternative splicing further reduces the level of functional transcripts. These results indicated that the short and distorted trichomes in Al might be caused by the suppression and alternative splicing of AlNAP1. Together, we revealed that AlNAP1 mediates trichome development and is a good candidate target for genetic modification of trichome length in kiwifruit.

Actinidiaceae, an economically important plant family, includes the Actinidia, Clematoclethra and Saurauia genus. Kiwifruit, with remarkably high vitamin C content, is an endemic species widely distributed in China with high economic value. Although many Actinidiaceae chloroplast genomes have been reported, few complete mitogenomes of Actinidiaceae have been studied. Here, complete circular mitogenomes of the four kiwifruit species and Saurauia tristyla were assembled. Codon usage, sequence repeats, RNA editing, gene transfers, selective pressure, and phylogenetic relationships in the four kiwifruit species and S. tristyla were comparatively analyzed. This research will contribute to the study of phylogenetic relationships within Actiniaceae and molecular barcoding in kiwifruit.

German chamomile (Matricaria chamomilla L.) and Roman chamomile (Chamaemelum nobile) are the two well-known chamomile species from the Asteraceae family. Owing to their essential oils and higher medicinal value, these have been cultivated widely across Europe, Northwest Asia, North America, and Africa. Regarding medicinal applications, German chamomile is the most commonly utilized variety and is frequently recognized as the “star among medicinal species”. The insufficient availability of genomic resources may negatively impact the progression of chamomile industrialization. Chamomile’s mitochondrial genome is lacking in extensive empirical research. In this study, we achieved the successful sequencing and assembly of the complete mitochondrial genome of M. chamomilla and C. nobile for the first time. An analysis was conducted on codon usage, sequence repeats within the mitochondrial genome of M. chamomilla and C. nobile. The phylogenetic analysis revealed a consistent positioning of M. chamomilla and C. nobile branches within both mitochondrial and plastid-sequence-based phylogenetic trees. Furthermore, the phylogenetic analysis also showed a close relationship between M. chamomilla and C. nobile within the clade comprising species from the Asteraceae family. The results of our analyses provide valuable resources for evolutionary research and molecular barcoding in chamomile.

The regulation of proline metabolism is critical for enhancing plant stress tolerance by promoting proline accumulation under abiotic stress conditions. Key enzymes in this pathway include Δ1-pyrroline-5-carboxylate synthase (P5CS), pyrroline-5-carboxylate reductase (P5CR), ornithine δ-aminotransferase (δ-OAT), proline dehydrogenase (PDH), and pyrroline-5-carboxylate dehydrogenase (P5CDH). Despite their importance, comprehensive identification and characterization of these gene families in kiwifruit (Actinidia chinensis) remain unexplored. This study identified two AcP5CSs, one AcP5CR, one AcOAT, three AcPDHs, and one AcP5CDH within the kiwifruit genome. This research comprehensively examined phylogenetic tree, gene structure, motif analysis, cis-regulatory elements and chromosomal distributions analysis, as well as expression profiles under abiotic stresses and hormonal stress. Under salt stress, transcriptional profiling showed marked upregulation of AcP5CS1, AcP5CR, and AcOAT, while AcP5CDH was significantly suppressed, as confirmed by qRT-PCR. Functional analysis demonstrated that AcP5CS1 overexpression in Arabidopsis significantly enhanced salt tolerance. The correlation results indicated a strong association between the AcNAC30 transcription factors (TFs) and the expression of AcP5CS1. Mechanistic studies using dual-luciferase and electrophoretic mobility shift assays (EMSA) confirmed that AcNAC30 directly binds to the AcP5CS1 promoter. Therefore, we speculated that AcNAC30 likely enhances proline accumulation under salt stress by upregulating the expression of proline metabolic pathway genes. These findings elucidate the genomic architecture of proline metabolic genes in kiwifruit and establish their pivotal role in mediating abiotic stress tolerance.

Baeckea frutescens Linaeus 1753, as a traditional folk medicine in South East Asia, possesses sesquiterpenes, phloroglucinols, chromones, and essential oil, and is utilized for traditional Chinese medicinal purposes. The genetic diversity of the plant must be better understood, considering its significance. The complete chloroplast (cp) genome of B. frutescens was sequenced and assembled by using Illumina paired-end data, marking a significant advancement toward comprehending its genetic composition. The complete cp genome is 158,939 bp in length and contains 128 genes, consisting of 83 protein-coding genes, 8 ribosomal RNA genes, and 37 transfer RNA genes. Phylogenetic analyses indicated that B. frutescens and other the 13 were clustered to the family of Myrtaceae. These findings are crucial for the conservation and utilization of this important plant species. Additionally, they underscore the potential for future research on the evolution and preservation of B. frutescens, which could be advantageous in pharmaceutical applications.