Influence of endogenous and exogenous RNases on the variation of pollen cytosolic-free Ca2+ in Pyrus serotina Rehd

The objective of this study was to examine whether S-RNase plays a specific role in the pre-germinated Pyrus pollen. Effects of exogenous RNase and endogenous S-RNase on concentration of cytosolic-free calcium (Ca²⁺]_i) variation of pre-germinated Pyrus pollen were studied. Ca²⁺]_i variation caused by different RNases were complex. In 1 h after being cultured, exogenous RNase, RNase T₁ and RNase A, and endogenous incompatible ‘Hohsui’ RNase promoted the Ca²⁺]_i of ‘Hohsui’ pollen. Acid proteins of ‘Hohsui’ had no remarkable influence on the Ca²⁺]_i of self-pollen. Endogenous compatible ‘Kohsui’ RNase reduced the Ca²⁺]_i of ‘Hohsui’ pollen, but compatible ‘Hohsui’ RNase can stimulate the Ca²⁺]_i of ‘Kohsui’ pollen. RNase T₁, RNase A and incompatible ‘Kohsui’ S-RNase can also make ‘Kohsui’ pollen Ca²⁺]_i increase. Different from ‘Hohsui’ pollen, acid proteins of ‘Hohsui’ pull down the ‘Kohsui’ pollen Ca²⁺]_i remarkably. Conclusion can be made that during the prophase of pollen germination, endogenous S-RNase has no specific effect on pollen Ca²⁺]_i changes.