ISSN:
1432-2048
Keywords:
Abscisic acid
;
Aleurone
;
Calcium transport
;
Endomembrane system
;
Gibberellin
;
Hordeum (Ca2+transport)
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract Gibberellic acid (GA3) and abscisic acid (ABA) regulate α-amylase production in aleurone tissue of the barley (Hordeum vulgare L.) grain during germination. Since α-amylase is a Ca2+-containing protein that is synthesized on the rough endoplasmic reticulum (ER), we investigated the possibility that GA3 and ABA regulate the flux of Ca2+ into the ER of aleurone cells. Membrane vesicles were isolated from GA3- and ABA-treated aleurone layers to characterize the effect of these hormones on calcium transport (CaT) activity as measured by the uptake of 45CaCl2 in vitro. We found that ABA and GA3 greatly alter the relative amounts of CaT activity in ER and tonoplast (TP) membrane fractions. Treatment with GA3 results in CaT being associated primarily with the ER, whereas treatment with ABA results in roughly equal amounts of CaT in ER and TP. Moreover, we found that ABA prevents or reverses the GA3-induced increase in CaT in the ER. The effects of ABA and GA3 on CaT in the ER require several hours to develop, and the effects of these hormones on CaT cannot be brought about by adding the hormones to membranes in vitro. In order to determine whether the in-vitro measurements of CaT reflect changes that occur in vivo we measured the Ca2+ content of isolated ER, measured Ca2+ transport into aleurone layers, and examined differences in the ability of ER proteins from GA- and ABA-treated layers to bind Ca2+. Our results indicate that GA3 increases and ABA decreases both Ca2+ flux into the ER and the amount of calcium that accumulates in the ER of barley aleurone cells in vivo.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00198213
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