農桿菌媒介轉殖法

Agrobacterium- Mediated Transformation

農桿菌是土壤中常見的植物病原菌，可透過和植物間遺傳物食之轉移，致使大多數雙子葉植物產生冠腫病。農桿菌需具備三個主要遺傳的成 分，始能達成植物細胞之轉殖：其一為會移動的DNA片段，簡稱為T-DNA＂但促使其移動的基因並不在於T-DNA片段上，而是位於Ti質體的致毒區域，此一區域為第二個主要遺傳成分，提供大部分T-DNA轉移所需之反式作用產物；第三成分是位於農捍菌染色體之基因座，這些基因主要參與農捍菌和植物細胞之結合。農桿菌媒介轉殖法已成功地應用在許多雙子葉植物上，但似乎並不適合所有植物，尤其是單子葉植物。藉由農桿菌感染是否可將外來基因導入穀類植物細胞中，早期也一直有相當地爭議。然而，近年來水稻等單子葉作物利用農桿菌進行轉殖之研究，展現了非常明確的遺傳和分子層次上之轉殖證據，同時也提供了其他單子葉植物藉由農桿菌媒介法，可達成轉殖目標的樂觀訊息。

Agrobacterium is a widespread soil plant pathogen that elicits tumors on most dicotyledonous plant through a navel interkingdom transfer of genetic information. Agrobacterium crries three genetic components that are required for plant cell transformation. The first component is the T-DNA fragment, which is the mobile DNA element. The second component is the element that mediates the transfer of the T-DNA fragment, which is located in the virlence region of the Ti plasmid. The virulence region provides most of the trans -acting products for T-DNA transit. The third component resides in the Agrobacterium chromosome. Genes contained in this component involve in attachment of Agrobacterium to plant cells. Agrobacterium- mediated transformation has been successfully applied in dicotyledons but not for monocotyledons, except in a few cases. Early studies of Agrobacterium -mediated transformation of cereal have been controversial because of lack of appropriate direct evidence. However, in recent years, genetic and molecular information provides clear evidence for the efficient transformation of rice mediated by Agrobacterium. This information suggests that Agrobacterium -mediated transformation of other monocotyle- donous species is possible.