Effects of postharvest storage and dormancy status on ABA content, metabolism, and expression of genes involved in ABA biosynthesis and metabolism in potato tuber tissues

Abstract

At harvest, and for an indeterminate period thereafter, potato tubers will not sprout and are physiologically dormant. Abscisic acid (ABA) has been shown to play a critical role in tuber dormancy control but the mechanisms controlling ABA content during dormancy as well as the sites of ABA synthesis and catabolism are unknown. As a first step in defining the sites of synthesis and cognate processes regulating ABA turnover during storage and dormancy progression, gene sequences encoding the ABA biosynthetic enzymes zeaxanthin epoxidase (ZEP) and 9-cis-epoxycarotenoid dioxygenase (NCED) and three catabolism-related genes were used to quantify changes in their relative mRNA abundances in three specific tuber tissues (meristems, their surrounding periderm and underlying cortex) by qRT-PCR. During storage, StZEP expression was relatively constant in meristems, exhibited a biphasic pattern in periderm with transient increases during early and mid-to-late-storage, and peaked during mid-storage in cortex. Expression of two members of the potato NCED gene family was found to correlate with changes in ABA content in meristems (StNCED2) and cortex (StNCED1). Conversely, expression patterns of three putative ABA-8'-hydroxylase (CYP707A) genes during storage varied in a tissue-specific manner with expression of two of these genes rising in meristems and periderm and declining in cortex during storage. These results suggest that ABA synthesis and metabolism occur in all tuber tissues examined and that tuber ABA content during dormancy is the result of a balance of synthesis and metabolism that increasingly favors catabolism as dormancy ends and may be controlled at the level of StNCED and StCYP707A gene activities.

Abscisic acid levels in tomato ovaries are regulated by LeNCED1 and SlCYP707A1

“…Here, we demonstrate that within 3 days the free-ABA content of pollinated tomato ovaries decreases to approximately 30% of that in unpollinated ovaries. A decrease in ABA concentration to 50 or 25% of the original concentration has also been measured in other physiological systems, such as in dormancy breakage in seeds (Chiwocha et al 2005) and tubers (Destefano-Beltran et al 2006). The relative decrease in ABA content in the tomato ovary is comparable to those observed in other processes in which ABA level is of physiological importance.…”

“…The localization of SlCYP707A1 mRNA is comparable to the localization of the hormone ABA in the ovules of Arabidopsis and cucumber (Peng et al 2006). The decrease in mRNA levels of the three other putative tomato CYP707A genes might be explained by the reduction in ABA concentration, since positive feedback from ABA on CYP707A expression has been found in Arabidopsis (Kushiro et al 2004;Umezawa et al 2006), potato (Destefano-Beltran et al 2006) and by us in tomato (Fig. 6b).…”

Regulation of potato tuber sprouting

“…At this time, ABA was named beta-inhibitor complex. Consistently, subsequent studies showed that ABA levels are highest in deeply dormant tubers and decline during storage (Korableva et al 1980;Biemelt et al 2000;Destefano-Beltran et al 2006b). In addition, treatment of microtubers with the ABA biosynthesis inhibitor fluridone reduced the ABA content significantly which was accompanied by a shortened dormancy period (Suttle and Hultstrand 1994).…”

Increasing of Food and Bioenergy Potato Resources by Microbial Influence on Tubers Phytohormonal Status

“…Induction of potato dormancy, inhibition of cell growth, stress resistance increase, accumulation of reserve substances in the resting organs are due to the presence of ABA [17]. Germination after deep dormancy is first of all due to an increase in the activity of auxins.…”