Nitric oxide modulates the influx of extracellular Capo and actin filament organization during cell wall construction in Pinus bungeana pollen tubes

摘要

Nitric oxide (NO) plays a key role in many physiological processes in plants, including pollen tube growth. Here, effects of NO on extracellular Capo flux and microfilaments during cell wall construction in Pinus bungeana pollen tubes were investigated. Extracellular Capo influx, the intracellular Capo gradient, patterns of actin organization, vesicle trafficking and cell wall deposition upon treatment with the NO donor S-nitroso-N-acetylpenicillamine (SNAP), the NO synthase (NOS) inhibitor Ns-nitro-L-arginine (L-NNA) or the NO scavenger 2-(4-carboxyphenyl)-4, 4, 5, 5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO) were analyzed. SNAP enhanced pollen tube growth in a dose-dependent manner, while L-NNA and cPTIO inhibited NO production and arrested pollen tube growth. Noninvasive detection and microinjection of a Capo indicator revealed that SNAP promoted extracellular Capo influx and increased the steepness of the tip-focused Capo gradient, while cPTIO and L-NNA had the opposite effect. Fluorescence labeling indicated that SNAP, cPTIO and L-NNA altered actin organization, which subsequently affected vesicle trafficking. Finally, the configuration and/or distribution of cell wall components such as pectins and callose were significantly altered in response to L-NNA. Fourier transform infrared (FTIR) microspectroscopy confirmed the changes in the chemical composition of walls. Our results indicate that NO affects the configuration and distribution of cell wall components in pollen tubes by altering extracellular Capo influx and F-actin organization.