Genomic characterization of a rare Carica papaya X chromosome mutant reveals a candidate monodehydroascorbate reductase 4 gene involved in all-hermaphrodite phenomenon.

Sex form is one of the most important characteristics in papaya cultivation in which hermaphrodite is the preferable form. Self-pollination of H*-TSS No.7, an inbred line derived from a rare X chromosome mutant SR*, produced all-hermaphrodite progeny. The recessive lethal allele controlling the all-hermaphrodite phenomenon was proposed to be the recessive Germination suppressor (gs) locus. This study employed next-generation sequencing technology and genome comparison to identify the candidate Gs gene. One specific gene, monodehydroascorbate reductase 4 (MDAR4) harboring a unique polymorphic 3 bp deletion in H*-TSS No.7 was identified. The function of MDAR4 is known to be involved in the hydrogen peroxide (H2O2) scavenging pathway and is associated with seed germination. Furthermore, MDAR4 showed higher expression in the imbibed seeds than that in the dry seeds indicating its potential role in the seed germination. Perhaps this is the very first report providing the evidences that MDAR4 is the candidate of Gs locus in H*-TSS No.7. In addition, Gs allele-specific markers were developed which would be facilitated for breeding all-hermaphrodite lines.

Molecular Dissection of Cucumis metuliferus Resistance against Papaya Ringspot Virus by Grafting.

Vegetable crops of the genus Cucumis are very popular worldwide and have great market value. However, their fruit quality and yield are hindered by viral diseases. C. metuliferus is considered a wild species with resistance to viral diseases that is lacking in cultivated crops of the Cucumis genus, such as melon. The C. metuliferus line L37 shows extreme resistance against Papaya ringspot virus (PRSV-HA), whereas line L35 is a susceptible line. In this study, reciprocal grafting experiments between L35 and L37 were performed, and the PRSV-HA strain was pre-inoculated in the rootstock leaves. The results revealed that the resistance signal in the L37 rootstock could transmit and provide resistance to the L35 scion. Subsequently, double sandwich grafting was performed using the pre-inoculated L35 as the rootstock, which was then grafted onto the L37 intermediate and the L35 scion. The results showed that PRSV-HA RNA accumulated in the L35 rootstock leaf, petiole, and stem tissues, whereas PRSV-HA RNA accumulated in some intermediate and scion petiole and stem tissues. No HCPro RNA was detected in the L35 scion leaves. The results showed that the suppression of the virus occurred in the leaves, and the resistance effect spread from the rootstock in the scion direction. Hence, this study has demonstrated that RNA silencing of systemic signals is responsible for L37 resistance against PRSV. C. metuliferus L37 could provide a valuable resistance source for crops of the Cucumis species against viral diseases through grafting.

The induction of orphan nuclear receptor Nur77 expression by n-butylenephthalide as pharmaceuticals on hepatocellular carcinoma cell therapy.

N-butylidenephthalide (BP), isolated from the chloroform extract of Angelica sinensis, has been examined for its antitumor effects on glioblastoma multiforme brain tumors; however, little is known about its antitumor effects on hepatocellular carcinoma cells. Two hepatocellular carcinoma cell lines, HepG2 and J5, were treated with either N-butylidenephthalide or a vehicle, and cell viability and apoptosis were evaluated. Apoptosis-related mRNA and proteins expressed, including orphan receptor family Nurr1, NOR-1, and Nur77, were evaluated as well as the effect of N-butylidenephthalide in an in vivo xenograft model. N-butylidenephthalide caused growth inhibition of both the cell lines at 25 microg/ml. Furthermore, N-butylidenephthalide-induced apoptosis seems to be related to Nur77 translocation from nucleus to cytosol, which leads to cytochrome c release and caspase-3-dependent apoptosis. N-butylidenephthalide-related tumor apoptosis was associated with phosphatidylinositol 3-kinase/protein kinase B (AKT)/glycogen synthase kinase-3beta rather than the mitogen-activated protein kinase or protein kinase C pathway. Blockade of AKT activation enhanced proliferation inhibition and the induction of phosphor-Bcl-2 and Nur77 proteins. Besides, the increasing apoptosis by BP via transfection wild-type cAMP-response element-binding protein (CREB) into tumor cell was suppressed by dominant phosphorylation site mutation of CREB. This finding suggested CREB pathway was also partly involved in tumor apoptosis caused by BP. Administration of N-butylidenephthalide showed similar antitumoral effects in both HepG2 and J5 xenograft tumors. N-Butylidenephthalide induced apoptosis in hepatocellular carcinoma cells, both in vitro and in vivo, suggesting a potential clinical use of this compound for improving the prognosis of hepatocellular carcinoma cells.