摘要
本文以拟南芥野生型Col-O以及光信号转导相关突变体hy5-215和copl-6为材料,研究了糖信号、光信号及赤霉素信号之间相互作用对拟南芥幼苗初生根生长的影响。研究结果为将来深入研究这些信号之间的相互关系奠定了一定的理论基础。主要研究结果总结如下：
在不同糖类(蔗糖、果糖和葡萄糖)中,蔗糖对拟南芥幼苗初生根生长的诱导作用最为明显。蔗糖可以在黑暗条件下诱导拟南芥幼苗初生根的生长,包括促进根的伸长以及根毛数量的增多；而在光下蔗糖的这种诱导作用不显著。光下用DCMU抑制拟南芥光合作用会完全抑制拟南芥初生根的生长；如果对被抑制光合作用的拟南芥幼苗用外源蔗糖处理,则可以恢复拟南芥幼苗根在光下的生长。以上这些结果说明在拟南芥幼苗初生根的生长过程中光合产物蔗糖有着不可替代的作用。
利用光信号转导相关突变体的研究发现光信号转导系统中HY5与COP1两种转录因子对拟南芥初生根的伸长和根毛数量的调节作用截然相反。HY5在光下负调节拟南芥初生根的伸长,正调节其根毛的数量；而COP1在光下正调节拟南芥初生根的伸长,负调节其根毛的数量。进一步研究发现,COP1对蔗糖所诱导的初生根的生长起负调节的作用；而HY5对蔗糖所诱导的初生根的生长起正调节作用。尤其是在黑暗条件下蔗糖诱导的copl-6突变体的根长以及根毛数量与Col-O相比具有显著的增加,而hy5-215突变体中表现出抑制作用。而且这些调节作用本身不会受到抑制光合作用处理的影响。光信号转导系统中的这两种转录因子对蔗糖所诱导的初生根生长的作用,说明光信号转导系统与蔗糖在拟南芥初生根生长中有交互作用。
用外源赤霉素(GAs)处理拟南芥(Col-O)幼苗不会影响其根的生长状态,但是如果抑制了拟南芥内源赤霉素生物合成,则会抑制拟南芥初生根的伸长,而且这种抑制作用会随着PAC(赤霉素生物合成抑制剂)浓度的增加而增加。不论是在光照还是黑暗条件下,赤霉素都会负调节拟南芥初生根根毛的数量。说明内源赤霉素在诱导拟南芥初生根生长过程中具有重要调节作用。PAC处理对hy5-215突变体根长基本没有影响；而PAC处理copl-6突变体幼苗,其根长会被抑制,并且这种抑制作用可被外源GA3所恢复。这些结果说明在拟南芥初生根的生长过程中,赤霉素通过HY5起作用。另外发现,GA3可以促进copl-6突变体根毛数量的增多,而且外源GA3可恢复PAC的抑制作用,GA3在copl-6突变体中诱导根毛数量增多的趋势与Col-O中的趋势是相反的,表明COP可能和GA3有直接或间接的相互作用。
Wild types Col-0 and hy5-215, cop1-6 mutants were used in this research to study the effects of the interaction of sugar signal, gibberellins signal and light signal on the primary roots growth of Arabidopsis seedlings. These primary results will lay a foundation for the theoretical formation of the more detailed mechanisms of the interactions of them. The following is the main results obtained from this study:
We found that sucrose rather than other sugars (glucose and fructose) has the best effect on induced the root growth of Arabidopsis. The growth of primary root could be inducted by sucrose in the dark, including elongation of primary root and increase of amount of root hair number. But such effect was not significant in light condition. The growth of primary root of Arabidopsis was almost suppressed completely in the presence of DCMU which could restraint photosynthesis of plants. We also found that exogenous application of sucrose could reverse the effect of DCMU. These results indicate that the photosynthesis is necessary for the growth of primary root of Arabidopsis seedlings.
The roles of HY5 and COP1 in induced root growth of Arabidopsis were also studied. The results showed that HY5 suppressed the elongation of primary root and stimulated the amount of root hair number. In contrast, COP1 stimulated the elongation of primary root and repressed the amount of root hair number. These data indicated that the regulations of the two light signal factors were exactly the opposite. We also found that sucrose is essential in the roles of HY5 and COP1 in Arabidopsis root growth. The amount of root hair number of cop1-6 mutants was significantly increased compared to that of Col-0 in the present of sucrose, especially in dark. And the inversed phenomena were observed in hy5-215 mutant. These results could not be affected by DCMU. The findings showed that there has crosstalk between the light signal transduction system and sucrose in the growth of primary root of Arabidopsis seedlings.
The application of exogenous gibberellins could not affect the root growth of Arabidopsis seedlings (Col-0). But the primary root length was suppressed in the application of paclobutrazol (PAC, a gibberellins biosynthesis inhibitor). And the suppression of PAC increased with its concentration increase. These results showed that gibberellins had a negative effect on the amount of root hair number and positive effect on primary root length of Arabidopsis both in light and dark condition. In present of PAC, the roots length of hy5-215 were not significantly changed, but the roots length of cop1-6 was suppressed. And exogenous GA3 application was able to reverse the repression caused by PAC. These data suggested that HY5 is required for GA3-indused root growth. Exogenous GA3 also could increase the amount of root hair number of cop 1-6 that different in wild type. Our data thus support a model that sucrose is a central role in induced root growth of Arabidopsis.
引文
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