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

Abstract

Phenylalanine ammonia-lyase (PAL; EC 4.3.1.5) catalyzes the first step in the synthesis of phenylpropanoids. An antisense or sense PAL cDNA of sweet potato under the control of a tapetum-specific promoter of rice was introduced into tobacco. A reduction in pollen fertility was observed in two out of seventeen antisense PAL 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 starch and flavonols. PAL activity in anthers at the microspore stage was also reduced to some extent and the level of PAL activity was positively correlated with the number of fertile pollen grains at the flowering stage. Although it was unclear how the antisense or sense transgene affected the PAL activity in anthers, our results clearly demonstrate that the PAL activity in the anther tapetum has a significant effect on the development of microspores.