Abstract
Nitric oxide (NO) plays essential roles in many biotic and abiotic stresses in plant development procedures, including pollen tube growth. Here, effects of NO on cold stress inhibited pollen germination and tube growth in Camellia sinensis were investigated in vitro. The NO production, NO synthase (NOS)-like activity, cGMP content and proline (Pro) accumulation upon treatment with NO scavenger cPTIO, NOS inhibitor L-NNA, NO donor DEA NONOate, guanylate cyclase (GC) inhibitor ODQ or phosphodiesterase (PDE) inhibitor Viagra at 25°C (control) or 4°C were analyzed. Exposure to 4°C for 2 h reduced pollen germination and tube growth along with increase of NOS-like activity, NO production and cGMP content in pollen tubes. DEA NONOate treatment inhibited pollen germination and tube growth in a dose-dependent manner under control and reinforced the inhibition under cold stress, during which NO production and cGMP content promoted in pollen tubes. L-NNA and cPTIO markedly reduced the generation of NO induced by cold or NO donor along with partly reverse of cold- or NO donor-inhibited pollen germination and tube growth. Furthermore, ODQ reduced the cGMP content under cold stress and NO donor treatment in pollen tubes. Meanwhile, ODQ disrupted the reinforcement of NO donor on the inhibition of pollen germination and tube growth under cold condition. Additionally, Pro accumulation of pollen tubes was reduced by ODQ compared with that receiving NO donor under cold or control condition. Effects of cPTIO and L-NNA in improving cold-treated pollen germination and pollen tube growth could be lowered by Viagra. Moreover, the inhibitory effects of cPTIO and L-NNA on Pro accumulation were partly reversed by Viagra. These data suggest that NO production from NOS-like enzyme reaction decreased the cold-responsive pollen germination, inhibited tube growth and reduced Pro accumulation, partly via cGMP signaling pathway in C. sinensis.
Highlights
Many plants have to cope with low temperature during their lifecycle and many physiological and molecular changes occur during cold acclimation [1]
We have found that pollen germination and tube elongation in C. sinensis were obviously inhibited by cold temperature
The inhibitory effects of DEA NONOate were contracted by Nitric oxide (NO) scavenger and NO synthase (NOS) inhibitor (L-NNA)
Summary
Many plants have to cope with low temperature during their lifecycle and many physiological and molecular changes occur during cold acclimation [1]. Exposure to cold acclimation significantly reduces the pollen germination rate [4] and alters the cellular organization in rice [5]. Many genes necessary for cold acclimation in vegetative tissues were either not or weekly induced in pollen under cold stress [4], indicating that the mechanism of cold tolerance is different in vegetative and reproductive tissues [7]. All those observations suggested that the understanding of the mechanism of Camellia pollen germination and tube growth resisting to cold stress warranted serious attention
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