Study On The Phytohormone Induce Character Of The NAC1 And The Function Of RSI-1 In Lateral Root Development

A huge root system can lead to high-resistance to stresses and high yield, while it is also a key dissimilatory organ and an extreme root mass can also result in excess energy consumption. As a result, techniques to bring a optimal root mass plays a leading role in crop tillage. The lateral root makes great part of the root system, and the lateral root primordia are the initial. The density of lateral root primordia emergence is usually determined by the express intensity of the key genes controlling the lateral root primordial initiation, while latter is controlled by its promoter. Therefore, characterization of the key genes controlling lateral root primordia initiation and researches of the genes in lateral root development may exert profound influence on manipulate root system development in crop culture.The research is consisted of two parts, and the first part is focus on character of the up-stream region of the NAC1. As an auxin early response gene, it can be induced by IAA and can mediate the auxin signal to promote the lateral root development. Researches show that NAC1 plays an important role in lateral root initiation, and its expression level has a strait effect on the emergence frequence of lateral root primordia. Computer based sequence analysis gives out that besides two auxin response elements local on the up-stream region, there still be several gibberellin response elements. The work here makes of NAC1 up-stream region cloneing, the express vector construction, tobacco transform; the marker gene express manner and the phytohormone induce effect analysis. Data not only verified the preceded result that NAC1 expressed specially in the division zone and in the lateral root primordial, its expression can be induced by auxin, but also show that it can expresses in the base of the lateral root and its expression can also be induced by gibberellin.The second part focused on the RSI-1 function on plant root development. The expression increasing and the enhancement of lateral root primordial emergency share the same manner as induced by auxin. Even more, the increase of RSI-1 transcripts is more early than the enhancement of the lateral root primordia emerge frequence. As a word, its expression and auxin inducing pattern make it like an 'Swithch point gene' in lateral root primordia development. In this part, an over-expression vector, an antisense express vector and an RNAi interference vector were constructed and transferred to tobacco, followed by genotype analysis of the transgenic plants. Result is that the T1 seedlings of the RSI-1 over-expression transformants show a decrease growth competence on 1/2 MS agar media and an increase ramification ability in the field. Evidence show that the RSI-1 protein may plays an role in the apical dominance controlling, and the chance of tobacco has a homologue gene with conserved nucleic sequence region to RSI-1 is slim. Anther possibility is that RSI-1 dose not works on the key point in the lateral root primordia initiation controlling network which is not consist with the result the author descript in the paper.The dissertation gives the works on the auxin and gibberellin induce effect of NAC1 and the phenotype changes in the transgenic tobacco with different vector induced in. The researches are some base works in trying to manipulate the crop root system development. The possibility of the two genes used in crop breedings and in new plant growth substance findings are alsodiscussed.