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 |
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Authors: | Luis Destefano-Beltrán Donna Knauber Linda Huckle Jeffrey C Suttle |
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Institution: | (1) United States Department of Agriculture, Agricultural Research Service, Sugarbeet and Potato Research Unit, Northern Crop Science Laboratory, 1307 18th Street N, State University Station, PO Box 5677, Fargo, ND 58105, USA |
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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
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Keywords: | ABA Dormancy Gene expression Potato Solanum tuberosum L Tuber qRT-PCR |
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