Expression Of Two Key Enzyme Genes In The Biosynthetic Pathway Of Ethylene In Sugarcane Leaves

The sugarcane were sprayed with 100mg/L of ethylene on the leaves at 5-6growth stage. After being treated, ethylene evolution, the net photosynthetic rate,content of chlorophyll in leaf and activities of enzymes related to sucrosemetabolism were measured; Four genes were used as probe gene in the pathway ofethylene biosynthesis to check the spatial and temporal diversity of expression onthe leaves at early growth stage; and the relationship between the expression of the4 genes and the effect of ethephon on production increasing was analysed. Thefollowings were the main results:1. During the early growth stage, there was slight but not significant differencein ethylene production among leaves in different position of both varieties of B1 andG17. the productivities were old leaf＞mature leaf＞young leaf. 100mg/L ethephonsignificantly increased the concentration of endogenous ethylene. The most effectwas occurred on young leaf in both varieties, as to mature and old leaf,increament effect is old leaf＞mature leaf in B1, while contrary effect in G17. Thepeak of ethylene release appeared on the 7th day after treatment in B1 mature leaf,while on the first day in G17.2. During the early growth stage, Net photosynthetic rate in both varieties of B1 and G17 was maintained at high level. 100mg/L ethephon significantly increasednot photosynthetic rate of two varieties. The peak of not photosynthetic rateappeared on the 28 day after treatment in B1 mature leaf, while on the 7th day inG17. Both of the retaining time and rate of increase of not photosynthetic rate in B1mature leaf was higher than that in G17.3. During the early growth stage, the chlorophyll a and chlorophyll a+b contentof the mature leaf in both varieties of B1 and G17 was maintained at higher leveland chlorophyll b content was maintained at lower level. 100mg/L ethephonsignificantly increased chlorophyll content of the mature leaf in both varieties. Thepeak of chlorophyll content appeared on the 7th day after treatment in B1 matureleaf, while on the third day in G17. Both of the retaining time and rate of increase ofnot photosynthetic rate in B1 mature leaf was higher than that in G17.4. During the early growth stage, there were differences in both of SS and SPSenzymes activities related to sucrose metabolism among leaves in different positionof two varieties of B1 and G17. The SS enzymes activitiesof B1 was maintained athigher level in mature leaf and at lower level in both of young leaf and old leaf,hower, which of G17 was maintained at higher level in both of young and matureleaf and at lower level in old leaf. The SPS enzymes activitiesof B1 was maintainedat higher level in both of mature and old leaf and at lower level in young leaf, but ascontrast for the variety G17. The peak of both enzymes activities appeared on thefirst day after treatment in B1 mature leaf, while on the third day in G17. 100mg/Lethephon significantly increased SS enzymes activities of the young and old leaf inboth varieties. For the mature leaf, ethephon showed inhabitation firstly and then improvement later on SS enzymes activities for two varieties. 100mg/L ethephonsignificantly increased SPS enzymes activities of old leaf in both varieties. The effectof ethephon on the young and mature leaf in different varieties was varied. For thevariety B1, ethephon significantly increased SPS enzymes activities of the young leaf,showed inhabitation firstly and then improvement later on SPS enzymes activities ofthe mature leaf. However, for the variety G17, ethephon inhibited SPS enzymesactivities of the young leaf and significantly increased SPS enzymes activities of themature leaf.5. Four genes of two key enzyme in the pathway of ethylene biosynthesis wereused as probe to check the effects of ethephon to the spatial and temporal diversityof expression on the leaves at early growth stage. The followings were the mainresults of Nothern blotting:Take Sc-ACS1 and Sc-ACS2 as the probe resectivily, both of the control andtreatment were examined hybrid signal, the signal degree was difference in varietiesand leaves. 100mg/L ethcphon significantly increased the expression of two genesin three leave position, especially in both position of mature leaf and old leaf,increament effect is old leaf＞mature leaf＞young leaf, which were in accordanceof the significant effect on increasing the ethylene production in the leave position.Take Sc-ACS3 as the probe, both of the control and treatment were notexamined hybrid signal, which was in accordance of the study that Sc-ACS3 was notexpressed in sugarcane leaves(Wang et al. 2006).Take GZ-ACO as the probe, both of the control and treatment were examinedhybrid signal,the signal degrees was difference in variety and leaf position. The expression of GZ-ACO gene was maintained at a higher level in leaves position oftwo varieties, 100mg/L ethephon significantly increased the expression of GZ-ACOgene in three leave position, especially in both position of mature and old leaf, whichwere in accordance of the significant effect on increasing the ethylene production inthe leave position.