植物不定根形成及其响应逆境胁迫的分子机制研究

Roots play a vital role in plant growth, development, and fitness. Many scientists are starting to see roots as central to their efforts to produce crops with a better yield - efforts that go beyond the Green Revolution. Roots are the key to a second green revolution - one that doesn't rely on expensive inputs. Roots can be divided into several categories depending on their origin and developmental history. Primary roots originate from the embryo in seeds, while lateral roots develop as branches of primary roots. Adventitious roots are distinct in that they develop ectopically from aboveground organs such as stems, often in situations where there is environmentally imposed stress. It is ecologically and evolutionarily significant of plants and a heritable quantitative trait that is affected by multiple endogenous and environmental factors, perhaps as an alternative or supplement to seed propagation in ecosystems where soil disturbance is frequent. Adventitious rooting is one of the most important ways of vegetative propagation in plants and one of the most important methods of commercial production of horticultural crops throughout the world. It is a prerequisite for the successful production of viable clones. However, the early molecular events under the early stage of adventitious rooting are poorly understood as yet. In this research being about to applying, we plan to investigate,using the approaches of molecular biology, the expression profiles of abiotic stress respones genes and auxin signaling response genes,such as ADH1, AHK, NHX1, RD22, RD29, ARL1, ARF7, ARF19, AUX1, LBD16, and LBD29, etc. during adventitious rooting in mung bean seedlings. We want further to investigate the expression alteration of these genes responding to the exogenous plant hormones and signaling molecules, such as IBA, ABA, BR(Brassinosteroids), ethylene, Ca2+, NO(nitric oxide), and H2O2, etc., the effects of the abiotic stresses, i.e. salinity, drought and heavy metal, on the genes expression and the induction of adventitious rooting, and the roles of the exogenous plant hormones and the signaling molecules in regulating these genes expression during adventitious rooting under abiotic stresses. The aim of this study is to elucidate the preliminary mechanisms on gene level invovled in adventitious rooting. The specific objectives are, (1) What relationships present between adventitious rooting and the stress response genes expression and auxin signaling response genes expression? (2)We want to know whether IBA, ABA, BR, ethylene, Ca2+, NO, and H2O2, affect adventitious rooting via regulating the genes expression; (3)How do the abiotic stresses change the genes expression further change adventitious rooting? and (4)How do IBA, ABA, BR, ethylene, Ca2+, NO, and H2O2 mediate adventitious rooting under the stresses via regulating the genes expression

不定根形成是植物无性繁殖的重要途径，具有重要经济意义；是环境胁迫下植物繁殖策略和对种子繁殖的补充，具有重要生态意义。目前在基因水平上对不定根形成机制的研究还很少开展。申请项目拟以绿豆为材料，运用生理生化和分子生物学方法，以基因ADH1、AHK、NHX1、RD22、RD29、ARL1、ARF7、ARF19、AUX1、LBD16和LBD29为指标，以绿豆幼苗不定根发生为实验模型，研究不定根形成过程及IBA、ABA、BR、乙烯、Ca2+、NO和H2O2处理，以及盐、渗透和重金属胁迫下不定根形成过程中基因表达的变化，揭示以下科学问题：(1)基因表达的变化与不定根形成之间关系；(2)植物生长调节物和信号分子对不定根形成的影响是如何通过基因表达的调控而实现的？(3)逆境胁迫是如何改变不定根形成中基因的表达而抑制根发生？(4)生长调节物和信号分子是如何通过调控基因表达促进不定根形成和对逆境胁迫的响应

不定根的形成是植物进行无性繁殖的重要途径，是在胁迫环境下植物的繁殖策略和对种子繁殖的补充。因此，具有重要的经济和生态意义。本项研究以绿豆为材料，建立绿豆幼苗下胚轴不定根形成实验模型，运用生理生化和分子生物学方法，开展了以下四方面研究：（1）植物不定根形成过程中胁迫响应基因和生长素信号途径基因表达水平的变化及其与不定根形成的关系的研究；（2）外源植物生长调节物和外源植物信号分子对植物不定根形成过程中胁迫响应基因和生长素信号途径基因表达调控的研究；（3）盐、渗透和重金属胁迫对植物不定根形成过程中胁迫响应基因和生长素信号途径基因表达的影响；（4）外源植物生长调节物和外源植物信号分子对胁迫下植物不定根形成过程中胁迫响应基因及生长素信号途径基因表达的影响。取得了以下重要研究结果：（1）首次鉴定出了绿豆中39个功能基因，即ARF1、ARF2、ARF3、ARF6、ARF8、ARF18、IAA8、IAA9、IAA14、IAA28、LAX4、PIN1、AUX15A、AUX22B、AUX22C、AUX22E、LBD16、LBD21、LBD29、LBD41、NHX2、NAC、NAC21、NAC25、NAC72、AHK1、AHK2、AHK3、RD22、PER1、PER2、QORL、MYB114、MYB134、ADH1、ADH1b、CPY20、eIF5A、ACTIN.（2）绿豆幼苗下胚轴不定根形成过程中，上述基因的表达发生了显著的变化。生长素促进不定根形成的分子机制在于：促进生长素信号途径基因的表达，起动生长素信号途径；促进胁迫应答基因的表达，提高细胞应对胁迫的能力；减缓氧化胁迫对细胞的影响。（3）分子机制上，NO和H2O2促进不定根的形成与生长素IBA存在相似之处，即：显著上调生长素信号途径和胁迫应答基因表达水平，显著下调抗氧化系统基因表达水平。（4）干旱、盐和重金属胁迫显著抑制绿豆幼苗不定根的形成，显著上调胁迫应答和抗氧化系统基因表达水平，表明胁迫对细胞产生了氧化胁迫。ABA降低细胞抗氧化系统活性，表明其对细胞的氧化胁迫具有减缓作用，提高细胞的耐受能力，部分地逆转胁迫对细胞的损伤而提高胁迫条件下不定根形成的能力。