GTP causes calcium release from a plant microsomal fraction

Area of Science:

• Plant Biology
• Cellular Physiology
• Biochemistry

Background:

• A GTP-specific calcium-releasing mechanism has been identified in non-mitochondrial, microsomal fractions of various animal cell types.
• This mechanism involves the release of calcium ions, a critical second messenger in cellular signaling.

Purpose of the Study:

• To investigate whether guanosine triphosphate (GTP) also induces calcium release from plant cellular fractions.
• To characterize the specificity and conditions of GTP-induced calcium release in zucchini (Cucurbita pepo L.) hypocotyl microsomes.

Main Methods:

• Isolation of a microsomal fraction from zucchini hypocotyls.
• Incubation of the microsomal fraction with varying concentrations of guanosine triphosphate (GTP).
• Measurement of calcium ion release using appropriate assays.

Main Results:

• GTP was found to induce rapid calcium release from zucchini hypocotyl microsomal fractions.
• Maximal calcium release was observed at 50 microM GTP, with half-maximal release at 8 microM.
• GTP's effect was highly specific, with other nucleotides (UTP, ATP, CTP, TTP, GMP) and non-hydrolyzable GTP analogues unable to induce release.
• Calcium reuptake was generally absent but could be induced by non-hydrolyzable GTP analogues, which also blocked subsequent GTP-induced release.

Conclusions:

• Guanosine triphosphate (GTP) plays a role in regulating calcium ions in plant cells, similar to its function in animal cells.
• The identified mechanism in zucchini hypocotyl microsomes points to a conserved signaling pathway involving GTP and calcium.
• Further research may explore the physiological relevance and regulatory roles of this GTP-dependent calcium signaling in plants.