Polyamine and ethylene interactions in grain filling of superior and inferior spikelets of rice |
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Authors: | Zhinqin Wang Yunji Xu Jingchao Wang Jianchang Yang Jianhua Zhang |
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Institution: | (1) Key Laboratory of Crop Genetics and Physiology of Jiangsu Province, Yangzhou University, Yangzhou, Jiangsu, China;(2) Department of Biology, Hong Kong Baptist University, Hong Kong, China; |
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Abstract: | This study was to test the hypothesis that polyamines (PAs) and ethylene and their interactions may be involved in mediating
the post-anthesis development of spikelets in rice (Oryza sativa L.). Six rice cultivars differing in grain filling rate were field-grown, and the changing patterns of PAs and ethylene levels
in rice spikelets during the filling and their relations with grain filling rates were investigated. The results showed that
inferior spikelets had much greater ethylene evolution rate and 1-aminocylopropane-1-carboxylic acid (ACC) concentration than
superior spikelets. Opposite to ethylene production, superior spikelets showed much higher free-spermidine (Spd) and free-spermine
(Spm) concentrations than inferior spikelets. Grain filling rate was very significantly and negatively correlated with ethylene
evolution rate and ACC concentration, whereas positively correlated with free-Spd and free-Spm concentrations and with the
ratio of free-Spd or free-Spm to ACC. Application of Spd, Spm, or aminoethoxyvinylglycine (an inhibitor of ethylene synthesis
by inhibiting ACC synthesis) to panicles at the early grain filling stage significantly reduced ethylene evolution rate and
ACC concentration, while significantly increased Spd and Spm concentrations, grain filling rate and grain weight of inferior
spikelets. Application of ACC, ethephon (an ethylene-releasing agent), or methylglyoxal-bis (guanylhydrazone) (an inhibitor
of Spd and Spm synthesis) showed the opposite effects. The results suggest that antagonistic interactions between PAs (Spd
and Spm) and ethylene may be involved in mediating grain filling. A higher ratio of free-Spd or free-Spm to ethylene in rice
spikelets could enhance grain filling. |
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