Calcium Requirement for Ethylene-Dependent Responses.

Area of Science:

• Plant Biology
• Plant Hormone Signaling
• Biochemistry

Background:

• Ethylene is a crucial plant hormone regulating development, defense, and fruit ripening.
• Ethylene perception involves a specific receptor, but downstream signaling pathways remain unclear.
• Plant pathogenesis response, like chitinase gene induction, serves as a model for studying ethylene signaling.

Purpose of the Study:

• To investigate the role of calcium in ethylene-dependent signal transduction pathways.
• To elucidate the necessity of calcium fluxes in ethylene-mediated plant responses.
• To understand calcium's involvement in ethylene's control over pathogenesis and growth.

Main Methods:

• Utilized the induction of pathogenesis-related gene chitinase as a model system.
• Manipulated calcium levels using chelators, ionophores (ionomycin), and pump blockers (thapsigargin).
• Assessed ethylene response in plants grown in calcium-deficient soil and restored sensitivity with calcium addition.

Main Results:

• Calcium fluxes are necessary for ethylene-dependent chitinase induction.
• Increased cytosolic calcium stimulated chitinase accumulation.
• Calcium-deficient plants showed impaired ethylene responses, including pathogenesis and abscisic acid-controlled guard cell closure.
• Restoring calcium levels in deficient plants re-established ethylene sensitivity.

Conclusions:

• Calcium is a critical component required for diverse ethylene-dependent processes in plants.
• Calcium acts as a necessary second messenger in ethylene signal transduction.
• Understanding calcium's role provides insights into plant hormone crosstalk and stress responses.