The miR159a-DUO1 module regulates pollen development by modulating auxin biosynthesis and starch metabolism in citrus.

Achieving seedlessness in citrus varieties is one of the important objectives of citrus breeding. Male sterility associated with abnormal pollen development is an important factor in seedlessness. However, our understanding of the regulatory mechanism underlying the seedlessness phenotype in citrus is still limited. Here, we determined that the miR159a-DUO1 module played an important role in regulating pollen development in citrus, which further indirectly modulated seed development and fruit size. Both the overexpression of csi-miR159a and the knocking out of DUO1 in Hong Kong kumquat (Fortunella hindsii) resulted in small and seedless fruit phenotypes. Moreover, pollen was severely aborted in both transgenic lines, with arrested pollen mitotic I and abnormal pollen starch metabolism. Through additional cross-pollination experiments, DUO1 was proven to be the key target gene for miR159a to regulate male sterility in citrus. Based on DNA affinity purification sequencing (DAP-seq), RNA-seq, and verified interaction assays, YUC2/YUC6, SS4 and STP8 were identified as downstream target genes of DUO1, those were all positively regulated by DUO1. In transgenic F. hindsii lines, the miR159a-DUO1 module down-regulated the expression of YUC2/YUC6, which decreased indoleacetic acid (IAA) levels and modulated auxin signaling to repress pollen mitotic I. The miR159a-DUO1 module reduced the expression of the starch synthesis gene SS4 and sugar transport gene STP8 to disrupt starch metabolism in pollen. Overall, this work reveals a new mechanism by which the miR159a-DUO1 module regulates pollen development and elucidates the molecular regulatory network underlying male sterility in citrus.

Evolution-guided multiomics provide insights into the strengthening of bioactive flavone biosynthesis in medicinal pummelo.

Pummelo (Citrus maxima or Citrus grandis) is a basic species and an important type for breeding in Citrus. Pummelo is used not only for fresh consumption but also for medicinal purposes. However, the molecular basis of medicinal traits is unclear. Here, compared with wild citrus species/Citrus-related genera, the content of 43 bioactive metabolites and their derivatives increased in the pummelo. Furthermore, we assembled the genome sequence of a variety for medicinal purposes with a long history, Citrus maxima 'Huazhouyou-tomentosa' (HZY-T), at the chromosome level with a genome size of 349.07 Mb. Comparative genomics showed that the expanded gene family in the pummelo genome was enriched in flavonoids-, terpenoid-, and phenylpropanoid biosynthesis. Using the metabolome and transcriptome of six developmental stages of HZY-T and Citrus maxima 'Huazhouyou-smooth' (HZY-S) fruit peel, we generated the regulatory networks of bioactive metabolites and their derivatives. We identified a novel MYB transcription factor, CmtMYB108, as an important regulator of flavone pathways. Both mutations and expression of CmtMYB108, which targets the genes PAL (phenylalanine ammonia-lyase) and FNS (flavone synthase), displayed differential expression between Citrus-related genera, wild citrus species and pummelo species. This study provides insights into the evolution-associated changes in bioactive metabolism during the origin process of pummelo.

Ethanol extract of Ilex hainanensis Merr. exhibits anti-melanoma activity by induction of G1/S cell-cycle arrest and apoptosis.

OBJECTIVE: To evaluate anti-melanoma effect of ethanol extract of Ilex hainanensis Merr. (IME) and elucidate its underlying mechanism. METHODS: Thirty-six tumor-bearing mice were randomized into 6 groups (n=6) as follows: model group, IME 25, 50, 100, and 200 mg/kg groups and dacarbazine (DTIC) 70 mg/kg group. The mice in the IME treatment groups were intragastrically administered with IME 25, 50, 100 or 200 mg/kg per day, respectively. The mice in the DTIC group were intraperitoneally injected with DTIC 70 mg/kg every 2 days. The drug administration was lasting for 14 days. The cell viability was evaluated by 3-(4,5-dime-thylthylthiazol-2-yl)-2, 5-diphenyl-tetrazolium bromide (MTT) assay. Flow cytometry was employed to detect cell cycle and apoptosis. The gene and protein expressions of nuclear factor κB-p65 (NF-κB-p65), Bcl-2, B-cell lymphomaextra large (Bcl-xL) and Bax were detected by quantitative real-time polymerase chain reaction and Western blot analyses. Caspases-3, -8, and -9 activities were detected using the colorimetric method. In addition, a B16-F10 melanoma xenograft mouse model was used to evaluate the anti-cancer activity of IME in vivo. Furthermore, a survival experiment of tumor-bearing mice was also performed to evaluate the possible toxicity of IME. RESULTS: IME significantly inhibited the proliferation of B16-F10 cells (P<0.01). Flow cytometric analysis showed that IME induced G1/S cell cycle arrest and apoptosis (both P<0.01). IME inhibited activation of NF-κB, decreased the gene and protein expressions of Bcl-2, Bcl-xL, and increased the gene and protein expressions of Bax (all P<0.01). In addition, IME induced the activation of Caspases-3, -8, and -9 in B16-F10 cells. The study in vivo showed that IME significantly reduced tumor volume (P<0.01), and the inhibitory rate came up to 68.62%. IME also induced large areas of necrosis and intra-tumoral apoptosis that correlated with a reduction in tumor volume. Survival experiment showed that treatment with IME for 14 days significantly prolonged survival time and 20% of mice in the IME 200 mg/kg group were still alive until the 50th day. Notably, IME showed no apparent side-effects during the treatment period. CONCLUSION: IME exhibited significant anti-melanoma activity in vitro and in vivo, suggesting that IME might be a promising effective candidate with lower toxic for malignant melanoma therapy.