Figure 4

Proposed pathways depicting effect of low dose (60 Gy) gamma radiation on shelf life extension of potato tubers under storage achieved by sprouting inhibition and extend dormancy. In brief, high level of ABA due to downregulation of ABA 8′-hydroxylase and upregulation of short chain alcohol dehydrogenase (SCAD) gene may lead to upregulation of ABA regulated gene like Glutaredoxin (Grx) which has been reported to negatively affect germination and seedling growth. Rate limiting step of ethylene biosynthesis from SAM via ACC is catalyzed by ACC synthase (ACS) was upregulated which may lead to high ethylene level and prolonged dormancy in irradiated potatoes. Upregulation of GH3 (Gretchen Hagen3) and auxin oxidase (peroxidase) as well as upregulation of repressor of early auxin response genes (ARP) may have also contributed to reduced auxin level and inhibition of sprout growth. Lower cytokinin due to down regulated tRNA-DMATase gene known to involve in its biosynthesis aided retained dormancy in irradiated potatoes. Furthermore, suppression of a number of genes related to cellular proliferation activities such as DNA synthesis, replication and cell division, translation and transcription machineries indicate reduction in metabolic activity and prolonged dormancy in radiation treated potato tubers. PAA: phenylacetic acid, IAA: indole acetic acid, GH3: Gretchen Hagen3, ARP: auxin repressed proteins, ARF: auxin response factors, ERF: ethylene response factor, SAM: S-adenosyl-l-methionine, ACC: 1-aminocyclopropane-1-carboxylic acid, ACO: 1-aminocyclopropane-1-carboxylic acid oxidase, GSH: glutathione, CDK: cyclin dependent kinase, APC: anaphase-promoting complex, DMATase: tRNA dimethyl allyl transferase, CK: cytokinin, GA: gibberellic acid, ABA: abscisic acid, SCAD: short chain alcohol dehydrogenase, CYP: cytochrome P450 mono-oxygenase, rNDP: ribonucleoside-diphosphate, Grx: glutaredoxin.