IPT b s low expression level in dwarfing rootstocks

IPT5b\'s low expression level in dwarfing rootstocks suggests its key role in regulating cytokinin biosynthesis (Fig. 1b). The known IPT proteins that are highly homologous to apple IPT5b were found in plants by homologous alignment (Fig. 2a), and further analysis indicated a common structural characteristic for the catalytic site of isopentenyltransferase (Fig. 2b). Grafting test showed that scion had no effect to the level of trans-zeatin or IPT5b expression to rootstocks (Supplemental Figs. 2a and 2b), further suggesting that poor root trans-zeatin biosynthesis may be an inherent characteristic in M9 rootstock caused by low IPT5b expression in root. Methylated CpGs can recruit transcriptional co-repressors to prevent transcription factors (TFs) from promoting gene expression by tightly packing CPI-455 structures [38]. Two CpG islands in the IPT5b promoter region showed higher methylation level in M9 rootstock compared to Mr (Fig. 3b). However, IPT5b expression was up-regulated in the root when treated with 5-azaC (Fig. 3e), suggesting that IPT5b expression is likely repressed by DNA methylation. Although, IPT5b expression in M9 rootstock increased upon treatment with 5-azaC, the levels were still lower than the Mr rootstock (Fig. 1, Fig. 3e), implying a limitation of the 5-azaC treatment, or there may be other mechanism that regulate IPT5b expression. In conclusion, we found low IPT5b expression and high levels of methylation in the IPT5b promoter region that correlated with low root trans-zeatin biosynthesis in M9 rootstock. Taken together, the methylation and subsequent lower IPT5b expression may induce dwarfing in the M9 rootstock.
Conflict of interest
Acknowledgements This project was partially supported by Special Fund for Agro-scientific Research in the Public Interest (201203075), the Earmarked Fund for China Agriculture Research System (CARS-28), National Key Technology Support Program (2013BAD02B01-4) and Beijing Collaborative Innovation Center for Eco-environmental Improvement with Forestry and Fruit Trees (CEFF-PXM2016-014207-000038).
Introduction Several strategies for targeted cancer therapy involving glucarpidase, also known as Carboxypeptidase G2 (CPG2), have been put into clinical practice in recent years [1]. (Glucarpidase or CPG2 will be used interchangeably throughout the text). Glucarpidase has proved particularly useful in Antibody Directed Enzyme Prodrug Therapy (ADEPT), in which it accumulates at the site of a tumor via a tumor-specific antibody, after that it converts a prodrug into an active drug [[2], [3], [4]]. In contrast, in cases of methotrexate-induced toxicity, glucarpidase is administered to convert this anti-cancer agent to a less harmful compound (4-deoxy-4-amino-N10-methylpteroic acid) that is excreted via a hepatic pathway. The enzyme is typically given in high doses to patients, thereby decreasing the risk of renal failure [[5], [6], [7], [8], [9]].