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ARS Home » Pacific West Area » Corvallis, Oregon » National Clonal Germplasm Repository » Research » Publications at this Location » Publication #226046
Title: Epigenetic Stability of Cryopreserved and Cold-Stored Hops

Author
item PEREDO, ELENA - UNIVERSIDAD DE OVIEDO
item ARROYO-GARCIA, ROSA - DEPT DE BIOTECNOLOGIA
item Reed, Barbara
item REVILLA, M. ANGELES - UNIVERSIDAD DE OVIEDO

Submitted to: Cryobiology
Publication Type: Abstract Only
Publication Acceptance Date: 2/20/2008
Publication Date: 2/20/2008
Citation: Peredo, E.L., Arroyo-Garcia, R., Reed, B.M., Revilla, M. 2008. Epigenetic Stability of Cryopreserved and Cold-Stored Hops. Cryobiology. 57:234-241.

Interpretive Summary: The genetic resources of hops are preserved as field plants and backed up for safety as tissue cultures in cold storage, or as cryopreserved shoot tips. This study was to determine if genetic changes occur with these procedures. Three hops cultivars were analyzed for genetic change after tissue culture, cold (45 °F) storage, and cryopreservation in liquid nitrogen (-320 °F). No genetic changes were noted but there were changes in gene expression. Most of this variation could be related to the cold storage or cryopreservation protocols. The pattern of change could be explained by temporary changes related to the cold acclimation step present in both treatments. Cold acclimation is a complex process, achieved by short day length and low temperatures, which results in the reprogramming of metabolism and gene expression. The amount of variation detected is similar for cold-stored (2.6 to 8.6%) or cryopreserved (2.6 to 9.8%) hops. Similar changes were reported in cryopreserved apple and strawberries and citrus callus under slow growth conditions. Cold acclimation was not used prior to the storage protocols for any of these studies.

Technical Abstract: Three hop accessions representative of commercially cultivated hops were selected for the analysis of epigenetic stability; females of different origins, including a cultivar developed in New Zealand (Calicross) from American cultivars, a landrace derived European cultivar (Tardif de Bourgogne), and a breeding accession (USDA 21055) obtained from crosses of English and American cultivars and wild American plants. Each accession included a total of five samples: one control, two cryopreserved samples and two samples kept under cold storage. The genetic stability of the accessions was previously assessed by RAPDs and AFLPs) (1)Cold acclimation, cryopreservation and cold storage method are described by Reed et al., 2003 (2). The MSAP analysis was performed according to Cervera et al., 1998 (3). Samples were electrophoresed in an automatic sequencer ABI PRISM® 3100 Genetic Analyzer and band patterns were analysed with the program Genemaper and corroborated by visual inspection of the electropherograms.Over 36% of the detected MSAP loci presented some sort of modification after cold storage or cryopreservation protocols. It is noticeable that over 87% of the total variation could be related to each or both protocols due to their presence in all the plants recovered from one or both procedures. Surprisingly the major part of the variation was shared by the cryopreserved and cold stored samples (50 to 72%) with demethylation the most frequent change comprising 27 to 45% of the total detected variation. On the other hand, different amounts of variation related to each specific treatment were found for every hop accession. Variation ranged from less than 8% in Calicross to around 20% in Tardif de Bourgogne. Nonetheless, in any of the cultivars the variation explained by the storing method was higher than the amount of variation shared by both treatments. This shared pattern could be explained by epigenetic changes related to the cold acclimation step present in both treatments. This consisted of a week or two of growth with temperature/photoperiod set of -1ºC 16h dark/ 22ºC 8h light. Cold acclimation is a complex process, achieved by short daylength and low temperatures, which results in the reprogramming of metabolism and gene expression. Cold stress regulates the plant transcriptome through transcriptional, post-transcriptional, and post-translational mechanisms which appear within hours of cold exposure. As there are exclusive methylation changes in the cold-stored plants or in the cryopreserved ones of each accession, we can assume that those treatments had at least some effects on the genome. The amount of variation detected is similar for cold-stored (2.6 to 8.6%) or cryopreserved (2.6 to 9.8%) hops. Methylation changes were reported in cryopreserved apple and strawberries (4,5) and citrus callus under slow growth (6). Cold acclimation was not used prior the storage protocols for any of these studies. 1. Peredo EL, Reed BM, García-Arroyo R and Revilla MA (2007) Abstracts of 871 COST Meeting, Oviedo University (Spain), pp. 52-53. 2. Reed BM, Okut N, D’Achino J, Narver L and DeNoma J (2003) Cryo-Lett 24:389-396. 3. Cervera MT, Cabezas JA, Sancha JC, Martínez de Toda F,Martínez-Zapater JM (1998) TAG 97:51–9. 4. Hao YJ, Liu QL and Deng, XX (2001) Cryobiology 43: 46-51 5. Hao YJ, You CX and Deng XX (2002) Cryo-Lett 23: 37-46 6. Hao YJ, Wen XP and Deng XX (2004) J Plant Physiol 161: 479-484