水稻种子成熟和萌发过程中脂氧合酶同工酶活性及其表达水平

水稻种子中有3种脂氧合酶（LOX）同工酶，分别为LOX-1、LOX-2、LOX-3。以本实验室筛选到的LOX-3缺失突变体北陆PL2和正常的水稻品种Koshihikari为材料，研究种子成熟及萌发过程中LOX活性的变化规律。结果显示，2个水稻品种在种子成熟中LOX活性变化规律不一致，Koshihikari开花后10～25d活性升高，以后趋于下降，而北陆PL2花后种子LOX活性基本没有变化；在种子萌发过程中两品种LOX活性变化规律基本一致，萌发初期活性迅速升高，浸水萌发后2d达到峰值，以后开始下降。同工酶分析、半定量RT-PCR结果都显示，在水稻成熟过程中，种子中LOX-3活性和表达水平都显著高于其他两种酶（LOX-1和LOX-2）；在种子萌发过程中，LOX-2活性和表达水平占优势，而LOX-1在种子成熟和萌发过程中都显示较低的活性和表达水平。这表明，水稻种子LOX-3可能与水稻的贮藏特性有关，LOX-2在水稻萌发过程中起主要作用，可能与水稻萌发期间储藏脂质的利用有关或者具有萌发信号的作用，而LOX-1的功能还有待进一步研究。

Analysis of lipoxygenase isozymes activity and expression level of rice seeds in developing and germinating stage

Three lipoxygenase isozymes, LOX-1, LOX-2 and LOX-3, were found in rice seeds. The variation of LOX activity during seed maturing and germinating was clarified, using Beilu PL2, deficient in LOX-3 found in our laboratory and wild type Koshihikari. The results showed that changes of LOX activity during seed maturing was different in two varieties. In Koshihikari LOX activity increased on day 10 -25 after flowering and then decreased slowly, whereas in Beilu PL2 there was no obvious change in LOX activity. Changes of LOX activity during seed germinating was similar in two varieties, LOX activity increased rapidly in the initial stage of seed germinating, peaked on 2nd day after germinating and thereafter declined. Further analysis by means of isozyme electrophoresis and semi quantitave RT-PCR indicated that expression level of LOX-3 was higher than that of the other two LOX considerably; meanwhile expression level of LOX-2 was primary during seed germinating and inferior during both periods for LOX-1. All these results showed that LOX-3 in rice seed was mainly involved in seed storage and LOX-2 in seed germinating, correlated with utilization of storage lipid in seeds during seed germinating or acted as signal for seed germinating, while accurate function of LOX-1 should be further studied.