Silencing of the Tapetum-Specific Zinc Finger Gene TAZ1 Causes Premature Degeneration of Tapetum and Pollen Abortion in Petunia

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Abstract
TAZ1 (TAPETUM DEVELOPMENT ZINC FINGER PROTEIN1; renamed from PEThy; ZPT3-2) cDNA was first isolated as an anther-specific cDNA from petunia. Here, we report a functional characterization that includes analysis of spatial and temporal expression profiles and examination of anther phenotypes in TAZ1-silenced plants. TAZ1 showed a biphasic expression pattern. In the premeiotic phase, TAZ1 transcripts were found to accumulate in all cell types of the anther except the tapetum and gametophytic tissues, whereas the postmeiotic phase of anther development was characterized by expression exclusively in the tapetum. Silencing of TAZ1 by cosuppression resulted in aberrant development and precocious degeneration of the tapetum, followed by extensive microspore abortion that started soon after their release from pollen tetrads. A few pollen grains that survived showed reduced flavonol accumulation, defects in pollen wall formation, and poor germination rates. This study demonstrates an essential role for TAZ1 in the postmeiotic phase of tapetum development.