<p style="text-align: justify;">The MS1 and RF1 canola lines (<i>Brassica napus</i>) were developed using genetic engineering techniques to provide a pollination control system for production of hybrid oilseed rape (MS1 x RF1). The novel hybridization system involves the use of two parental lines, a male sterile line MS1 and a fertility restorer line RF1. The transgenic MS1 plants do not produce viable pollen grains and cannot self-pollinate. In order to completely restore fertility in the hybrid progeny, line MS1 must be pollinated by a modified plant containing a fertility restorer gene, such as line RF1. The resultant F1 hybrid seed derived from cross between MS1 x RF1, produces hybrid plants that produce pollen and are completely fertile.</p>

<p style="text-align: justify;">The transgenic line MS1 (B91-4) was produced by genetically engineering plants to be male sterile and tolerant to the herbicide glufosinate ammonium (as a selectable marker). The parental line MS1 contains the <i>barnase</i> gene for male sterility, isolated from <i>Bacillus amyloliquefaciens</i>, a common soil bacterium that occurs naturally in the soil and in various organisms including bacteria and plants, and frequently used as a source for industrial enzymes. The <i>barnase</i> gene encodes for a ribonuclease enzyme (RNAse) 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.</p>

<p style="text-align: justify;">The transgenic line RF1 (B93-101) 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 RF1 plants contain the <i>barstar</i> gene isolated from <i>Bacillus amyloliquefaciens</i>. The <i>barstar</i> gene codes for a ribonuclease inhibitor (barstar enzyme) expressed only in the tapetum cells of the pollen sac during anther development. The ribonuclease inhibitor (barstar enzyme) specifically inhibits barnase RNAse expressed by the MS1 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 RF1 is crossed to the male sterile line MS1, the resultant progeny express the RNAse inhibitor in the tapetum cells of the anthers allowing hybrid plants to develop normal anthers and restore fertility.<br />
Both trangenic canola lines MS1 and RF1 contain the <i>bar</i> gene that confers tolerance to the post-emergence, broad-spectrum phosphinothricin herbicides (Liberty&reg;). 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 ammounium 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 cells in the laboratory, and as a field selection method to obtain 100% hybrid seed.</p>
