Auxin guides germ-cell specification in Arabidopsis anthers

Prof. Shunong Bai published a paper in PNAS with his collaborators.

Germ cells (GCs) transmit genetic information from one generation to the next. Unlike animal  GCs, plant GCs are induced post-embryonically, forming locally from somatic cells. This  induction is coordinated with organogenesis and might be guided by positional cues. In  angiosperms, male GCs initiate from the internal layers at the four corners of the anther  primordia and are gradually enclosed by parietal cell (PC) layers, leading to a concentric GC[1]PC pattern.^1,2 However, the underlying mechanism of GC initiation and GC-PC pattern formation is unclear. Auxin affects pattern formation³ and anther development.^4–11 However, whether GC formation involves auxin remains unknown. We report that the auxin distribution in pre-meiotic anthers parallels GC initiation, forming a centripetal gradient between the outer primordial cells and the inner GCs. The auxin biosynthesis genes TRYPTOPHAN AMINOTRANSFERASE OF ARABIDOPSIS 1 (TAA1) and TRYPTOPHAN AMINOTRANSFERASE RELATED 2 (TAR2)^5,12 are responsible for this patterning and  essential for GC specification. SPOROCYTELESS/NOZZLE (SPL/NZZ, a determinant for GC specification)^13–15 mediates the effect of auxin on GC specification, modulates auxin homeostasis, and maintains centripetal auxin patterning. Our results reveal that auxin is a key factor guiding GC specification in Arabidopsis anthers.