Spatio-Temporal Accumulation and Activity of Calcium-Dependent Protein Kinases during Embryogenesis, Seed Development, and Germination in Sandalwood

Abstract

Western-blot analysis and protein kinase assays identified two Ca 2؉ -dependent protein kinases (CDPKs) of 55 to 60 kD in soluble protein extracts of embryogenic cultures of sandalwood (Santalum album L.). However, these sandalwood CDPKs (swCDPKs) were absent in plantlets regenerated from somatic embryos. swCDPKs exhibited differential expression (monitored at the level of the protein) and activity in different developmental stages. Zygotic embryos, seedlings, and endosperm showed high accumulation of swCDPK, but the enzyme was not detected in the soluble proteins of shoots and flowers. swCDPK exhibited a temporal pattern of expression in endosperm, showing high accumulation and activity in mature fruit and germinating stages; the enzyme was localized strongly in the storage bodies of the endosperm cells. The study also reports for the first time to our knowledge a post-translational inhibition/inactivation of swCDPK in zygotic embryos during seed dormancy and early stages of germination. The temporal expression of swCDPK during somatic/zygotic embryogenesis, seed maturation, and germination suggests involvement of the enzyme in these developmental processes.

Calcium-Dependent Protein Kinase Isoforms inPetuniaHave Distinct Functions in Pollen Tube Growth, Including Regulating Polarity

“…CDPK isoforms localize to a variety of intracellular locations, including the cytosol, nucleus, plasma membrane, endoplasmic reticulum, peroxisomes, mitochondrial outer membrane, and oil bodies (Pical et al, 1993;Patharkar and Cushman, 2000;Lu and Hrabak, 2002;Anil et al, 2003;Dammann et al, 2003). We employed confocal microscopy to assess the subcellular localization of each CDPK isoform using full-length C-terminal GFP fusions.…”

Calcium-dependent protein phosphorylation in hairy roots of Daucus carota

“…Each point represents an average value from at least 20 segments, with standard errors as indicated. Harmon et al 2000, Pandey et al 2000, Reddy 2001, Cheng et al 2002, Nayyar 2003, Malho et al 2006. However, there have been no reports of CDPK or protein phosphorylation by CDPK influencing growth in plants.…”

Analysis of the Complexity of Protein Kinases within the Phloem Sieve Tube System

“…2D). The soybean CDPK␣ antibody, which has been used to identify CDPK isoforms from various plants (17,25,26), recognized only the protein kinase eluted at the higher salt concentration. To confirm that this protein kinase is a CDPK, we next tested its Ca 2ϩ binding capacity by gel mobility shift assay.…”