Partial Male Sterility in Transgenic Tobacco Carrying Antisense and Sense PAL cDNA under the Control of a Tapetum-Specific Promoter

Phenylalanine ammonia-lyase (PAL; EC 4.3.1.5 EC] ) catalyzes thefirst step in the synthesis of phenylpropanoids. An antisenseor sense PAL cDNA of sweet potato under the control of a tapetum-specificpromoter of rice was introduced into tobacco. A reduction inpollen fertility was observed in two out of seventeen antisensePAL transformants and in six out of nineteen sense PAL transformants.The pollen fertility of these plants ranged from 8% to 60%.The distorted pollen grains that did not germinate lacked starchand flavonols. PAL activity in anthers at the microspore stagewas also reduced to some extent and the level of PAL activitywas positively correlated with the number of fertile pollengrains at the flowering stage. Although it was unclear how theantisense or sense transgene affected the PAL activity in anthers,our results clearly demonstrate that the PAL activity in theanther tapetum has a significant effect on the development ofmicrospores. (Received October 9, 1995; Accepted March 10, 1996)