Overexpression of TCP5 or Its Dominant Repressor Form, TCP5-SRDX, Causes Male Infertility in Arabidopsis

TCP transcription factors have long been known to play a crucial role in leaf development, but their significance in reproduction has recently been revealed. TCP5 is a member of class II of the TCP family, which predominantly regulates cell differentiation. This study used overexpression and SRDX fusion to evaluate the role of TCP5 in anther development. <i>TCP5</i> overexpression resulted in lower fertility, primarily due to anther non-dehiscence. We also observed reduced lignin accumulation in the anther endothecium. In addition, <i>TCP5</i> overexpression resulted in smaller anthers with fewer pollen sacs and pollen due to early-anther defects before meiosis. <i>TCP5</i> showed expression in early anthers, including the epidermis, endothecium, middle layer, tapetum, sporogenous cells (pollen mother cells), and vascular bundles. Conversely, during meiosis, the <i>TCP5</i> signal was only detected in the tapetum, PMCs, and vascular bundles. The <i>TCP5</i> signal disappeared after meiosis, and no signal was observed in mature anthers. Interestingly, the <i>TCP5-SRDX</i> transgenic plants were also sterile, at least for the early-arising flowers, if not all of them. <i>TCP5-SRDX</i> expression also resulted in undersized anthers with fewer pollen sacs and pollen. However, the lignin accumulation in most of these anthers was comparable to that of the wild type, allowing these anthers to open. The qRT-PCR results revealed that several genes associated with secondary cell wall thickening had altered expression profiles in <i>TCP5</i> overexpression transgenics, which supported the non-dehiscent anther phenotype. Furthermore, the expression levels of numerous critical anther genes were down-regulated in both <i>TCP5</i> overexpression and <i>TCP5-SRDX</i> plants, indicating a comparable anther phenotype in these transgenic plants. These findings not only suggest that an appropriate <i>TCP5</i> expression level is essential for anther development and plant fertility, but also improve our understanding of TCP transcription factor functioning in plant male reproduction and contribute information that may allow us to manipulate fertility and breeding in crops.