Expression of the high capacity calcium-binding domain of calreticulin increases bioavailable calcium stores in plants.

Modulation of cytosolic calcium levels in both plants and animals is achieved by a system of Ca2+-transport and storage pathways that include Ca2+ buffering proteins in the lumen of intracellular compartments. To date, most research has focused on the role of transporters in regulating cytosolic calcium. We used a reverse genetics approach to modulate calcium stores in the lumen of the endoplasmic reticulum. Our goals were two-fold: to use the low affinity, high capacity Ca2+ binding characteristics of the C-domain of calreticulin to selectively increase Ca2+ storage in the endoplasmic reticulum, and to determine if those alterations affected plant physiological responses to stress. The C-domain of calreticulin is a highly acidic region that binds 20-50 moles of Ca2+ per mole of protein and has been shown to be the major site of Ca2+ storage within the endoplasmic reticulum of plant cells. A 377-bp fragment encoding the C-domain and ER retention signal from the maize calreticulin gene was fused to a gene for the green fluorescent protein and expressed in Arabidopsis under the control of a heat shock promoter. Following induction on normal medium, the C-domain transformants showed delayed loss of chlorophyll after transfer to calcium depleted medium when compared to seedlings transformed with green fluorescent protein alone. Total calcium measurements showed a 9-35% increase for induced C-domain transformants compared to controls. The data suggest that ectopic expression of the calreticulin C-domain increases Ca2+ stores, and that this Ca2+ reserve can be used by the plant in times of stress.
AuthorsSarah E Wyatt, Pei-Lan Tsou, Dominique Robertson
JournalTransgenic research (Transgenic Res) Vol. 11 Issue 1 Pg. 1-10 (Feb 2002) ISSN: 0962-8819 [Print] Netherlands
PMID11874098 (Publication Type: Journal Article, Research Support, U.S. Gov't, Non-P.H.S.)
Chemical References
  • Calcium-Binding Proteins
  • Calreticulin
  • Luminescent Proteins
  • Ribonucleoproteins
  • Green Fluorescent Proteins
  • Calcium
  • Agrobacterium tumefaciens (genetics)
  • Arabidopsis (genetics, growth & development)
  • Biological Availability
  • Calcium (metabolism)
  • Calcium-Binding Proteins (chemistry, metabolism)
  • Calreticulin
  • Genetic Vectors
  • Green Fluorescent Proteins
  • Luminescent Proteins (genetics)
  • Phenotype
  • Plants, Genetically Modified
  • Ribonucleoproteins (chemistry, metabolism)
  • Zea mays (genetics, metabolism)

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