<p style="text-align: justify;">The MS8 and RF3 canola lines (<i>Brassica napus</i>) were developed using genetic engineering techniques to provide a pollination control system for production of hybrid oilseed rape (MS8 x RF3). The novel hybridization system involves the use of two parental lines, a male sterile line MS8 and a fertility restorer line RF3. The transgenic MS8 plants do not produce viable pollen grains and cannot self-pollinate. In order to completely restore fertility in the hybrid progeny, line MS8 must be pollinated by a modified plant containing a fertility restorer gene, such as line RF3. The resultant F1 hybrid seed derived from cross between MS8 x RF3, produces hybrid plants that produce pollen and are completely fertile.</p>

<p style="text-align: justify;">The transgenic line MS8 (DBN230-0028) was produced by genetically engineering plants to be male sterile and tolerant to the herbicide glufosinate ammonium (as a selectable marker). The parental line MS8 contains the barnase gene for male sterility, isolated from <i>Bacillus amyloliquefaciens</i>, a common soil bacterium that occurs naturally in the soil and is frequently used as a source for industrial enzymes. The barnase gene encodes for a ribonuclease enzyme (RNAse) that is expressed only in the tapetum cells of the pollen sac during anther development. The RNAse affects RNA production, disrupting normal cell functioning and arresting early anther development, thus leading to male sterility.<br />
The transgenic line RF3 (DBN212-0005) was produced by genetically engineering plants to restore fertility in the hybrid line and to be tolerant to the herbicide glufosinate ammonium (as a selectable marker). Transgenic RF3 plants contain the barstar gene isolated from <i>Bacillus amyloliquefaciens</i>. The barstar gene codes for a ribonuclease inhibitor (barstar enzyme) that is expressed only in the tapetum cells of the pollen sac during anther development. The ribonuclease inhibitor specifically inhibits barnase RNAse expressed by the MS8 line. Together, the RNAse and the ribonuclease inhibitor form a very stable one-to-one complex, in which the RNAse is inactivated. As a result, when pollen from the restorer line RF3 is transferred to the male sterile line MS8, the resultant progeny express the RNAse inhibitor in the tapetum cells of the anthers allowing hybrid plants to develop normal anthers and restore fertility.</p>

<p style="text-align: justify;">Both trangenic canola lines MS8 and RF3 contain the <i>bar</i> gene that confers tolerance to the post-emergence, broad-spectrum phosphinothricin herbicides (Basta, Rely, Finale, and Liberty). The <i>bar</i> gene, isolated from the common soil microorganism <i>Streptomyces hygroscopicus</i> encodes a phosphinothricin acetyl transferase (PAT) enzyme. The active ingredient in phosphinothricin herbicides is glufosinate ammonium which acts by inhibiting the plant enzyme glutamine synthetase, leading to the accumulation of phytotoxic levels of ammonia killing the plant within hours of application. PAT detoxifies glufosinate ammonium by acetylation into an inactive compound, eliminating its herbicidal activity. The herbicide tolerance trait was introduced into the canola lines as a selectable marker to identify transformed plants during tissue culture regeneration, and as a field selection method to obtain 100% hybrid seed.</p>
