title: Cereal cystatins delay sprouting and nutrient loss in tubers of potato, Solanum tuberosum.
abstract: BACKGROUND
  Recent studies have reported agronomically useful ectopic effects for recombinant protease inhibitors expressed in leaves of transgenic plants, including improved tolerance to abiotic stress conditions and partial resistance to necrotrophic pathogens. Here we assessed the effects of these proteins on the post-dormancy sprouting of storage organs, using as a model potato tubers expressing cysteine protease inhibitors of the cystatin protein superfamily.
  
  
  RESULTS
  Sprout emergence and distribution, soluble proteins, starch and soluble sugars were monitored in tubers of cereal cystatin-expressing clones stored for several months at 4 °C. Cystatin expression had a strong repressing effect on sprout growth, associated with an apparent loss of apical dominance and an increased number of small buds at the skin surface. Soluble protein content remained high for up to 48 weeks in cystatin-expressing tubers compared to control (untransformed) tubers, likely explained by a significant stabilization of the major storage protein patatin, decreased hydrolysis of the endogenous protease inhibitor multicystatin and low cystatin-sensitive cysteine protease activity in tuber tissue. Starch content decreased after several months in cystatin-expressing tubers but remained higher than in control tubers, unlike sucrose showing a slower accumulation in the transgenics. Plantlet emergence, storage protein processing and height of growing plants showed similar time-course patterns for control and transgenic tubers, except for a systematic delay of 2 or 3 d in the latter group likely due to limited sprout size at sowing.
  
  
  CONCLUSIONS
  Our data point overall to the onset of metabolic interference effects for cereal cystatins in sprouting potato tubers. They suggest, in practice, the potential of endogenous cysteine proteases as relevant targets for the development of potato varieties with longer storage capabilities.
authors.affiliation: Centre de recherche et d'innovation sur les végétaux|Biotechnologie Université Laval, Québec, QC, G1V 0A6, Canada. aurelie.munger.1@ulaval.ca.
authors.forename: Aurélie
authors.initials: A
authors.lastname: Munger
authors.affiliation: Centre de recherche et d'innovation sur les végétaux|Biotechnologie Université Laval, Québec, QC, G1V 0A6, Canada. msimon@cstj.qc.ca.|Present address: Services aux entreprises et formation continue, Cégep de St-Jérôme, St-Jérôme, J7Z 4 V2, QC, Canada. msimon@cstj.qc.ca.
authors.forename: Marie-Aube
authors.initials: MA
authors.lastname: Simon
authors.affiliation: Centre de recherche et d'innovation sur les végétaux|Biotechnologie Université Laval, Québec, QC, G1V 0A6, Canada. khalafm1@hotmail.com.
authors.forename: Moustafa
authors.initials: M
authors.lastname: Khalf
authors.affiliation: Centre de recherche et d'innovation sur les végétaux|Biotechnologie Université Laval, Québec, QC, G1V 0A6, Canada. marie-claire.goulet@fsaa.ulaval.ca.
authors.forename: Marie-Claire
authors.initials: MC
authors.lastname: Goulet
authors.affiliation: Centre de recherche et d'innovation sur les végétaux|Biotechnologie Université Laval, Québec, QC, G1V 0A6, Canada. dominique.michaud@fsaa.ulaval.ca.
authors.forename: Dominique
authors.initials: D
authors.lastname: Michaud
mesh_terms: D015891:Cystatins / Q000235:genetics* / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D018525:Germination; D012275:Oryza / Q000235:genetics* / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D035281:Plant Tubers / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D011198:Solanum tuberosum / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D003313:Zea mays / Q000235:genetics* / Q000378:metabolism
chemical_list: D015891:Cystatins; D010940:Plant Proteins; C077834:cystatin protein, Zea mays