The peel color of pomegranates is an important exterior quality that determines market value. Anthocyanins are biosynthesized in the cytosol and then transported to the vacuole for storage. However, the molecular mechanism that determines the color variation between red and white pomegranates remains unclear. In this study, we identified an R2R3-MYB protein (PgMYB1) that interacts with the PgGSTF6 promoter and regulates its transcriptional expression, thus promoting the accumulation of anthocyanins in pomegranate. The expression of PgMYB1 and PgGSTF6 was positively correlated with the anthocyanin content in red and white pomegranates. Further investigation showed that the knockdown of PgMYB1 in red pomegranate ‘Taishanhong’ (TSH), by the virus-induced gene-silencing system, inhibited anthocyanin accumulation. Together, our results indicate that PgMYB1 controls the transport of anthocyanin via PgGSTF6 and thus promotes anthocyanin accumulation in red pomegranates. Our results have a certain reference value for further clarifying the regulation of anthocyanin synthesis and transport in pomegranate fruits.

Cold stress is a significant factor limiting plant growth and development. Pomegranate is particularly susceptible to low temperatures. Calmodulin-binding transcriptional activators (CAMTAs) are key regulators of cold stress tolerance in plants. In this study, we conducted a comprehensive analysis of the CAMTA family proteins across 12 species, including Punica granatum (pomegranate), using bioinformatic methods. Pomegranate CAMTA3 (PgCAMTA3) was isolated and characterized, and it demonstrated enhanced cold tolerance when expressed in Arabidopsis thaliana. Quantitative real-time PCR (qRT-PCR) analysis showed that the expression of PgCAMTA3 was up-regulated under cold and ABA treatments in pomegranates. Two A. thaliana transgenic lines, OE1 and OE2, which overexpress PgCAMTA3, were generated through genetic transformation. The overexpression of PgCAMTA3 enhanced the cold stress tolerance in transgenic A. thaliana. OE1 and OE2 exhibited higher survival rates under cold stress. Furthermore, enzymatic activity assays revealed enhanced peroxidase (POD), catalase (CAT), and superoxide dismutase (SOD) in OE lines. These antioxidant enzymatic activities collectively contribute to better cold stress tolerance by providing more effective reactive oxygen species (ROS) scavenging and cellular protection mechanisms, which was confirmed by lower levels of malondialdehyde (MDA) and ROS production. In addition, the overexpression of PgCAMTA3 led to the upregulation of the expression levels of AtCBF2, AtNCED3, and AtWRKY22, which were modulated by CAMTA3. In summary, we report the significant role of PgCAMTA3 in plant cold tolerance. Our findings provide valuable insights into the CAMATA family in plants and offer new perspectives on the molecular mechanisms underlying cold tolerance in pomegranates.

Malus spectabilis ‘Guanghui’ is an important ornamental plant, which complete chloroplast genome (Accession: MT501657) was sequenced, assembled and annotated. The genome size is 1601,230 bp and the overall GC content is 36.50%, with large single-copy (LSC, 89,310bp) regions, small single-copy (SSC, 19,196 bp) regions, and two inverted repeat regions (IRs, 23,632bp each). A total of 129 genes are successfully annotated, including 84 protein-coding genes, 37 tRNA genes, and 8 rRNA genes. The phylogenetic relationships showed that Malus spectabilis ‘Guanghui’ is closely related to the species of Malus sieversii.

Hovenia acerba Lindl. is an important medicinal plant, for which complete chloroplast genome (Accession: MN782301) was sequenced, assembled and annotated. The genome size is 161,668 bp and the overall GC content is 36.69%, with large single-copy (LSC, 89,451bp) regions, small single-copy (SSC, 18,979 bp) regions, and two inverted repeat regions (IRs, 26,619 bp each). A total of 130 genes are successfully annotated, including 85 protein-coding genes, 37 tRNA genes, and 8 rRNA genes. The phylogenetic relationships showed that H. acerba is closely related to the species of Ziziphus genus.