Auxin guides germ-cell specification in Arabidopsis anthers

Abstract

Germ cells (GCs) are the key carriers delivering genetic information from one generation to the next. In a majority of animals, GCs segregate from somatic cells during embryogenesis by forming germlines. In land plants, GCs segregate from somatic cells during postembryonic development. In a majority of angiosperms, male GCs (archesporial cells) initiate at the four corners of the anther primordia. Little is known about the mechanism underlying this initiation. Here, we discovered that the dynamic auxin distribution in developing anthers coincided with GC initiation. A centripetal auxin gradient gradually formed toward the four corners where GCs will initiate. Local auxin biosynthesis was necessary for this patterning and for GC specification. The GC determinant protein SPOROCYTELESS/NOZZLE (SPL/NZZ) mediated the effect of auxin on GC specification and modified auxin biosynthesis to maintain a centripetal auxin distribution. Our work reveals that auxin is a key factor guiding GC specification in Arabidopsis anthers. Moreover, we demonstrate that the GC segregation from somatic cells is not a simple switch on/off event but rather a complicated process that involves a dynamic feedback circuit among local auxin biosynthesis, transcription of SPL/NZZ, and a progressive GC specification. This finding sheds light on the mystery of how zygote-derived somatic cells diverge into GCs in plants.

New Insights Into the Local Auxin Biosynthesis and Its Effects on the Rapid Growth of Moso Bamboo (Phyllostachys edulis)

“…After incubation, the samples were washed two or three times in 10 mM phosphate buffer and 0.1% (vol.vol −1 ) BSA for 10 min at a time and then washed with 10 mM phosphate-buffered saline (PBS) and 0.8% (wt.vol −1 ) BSA for 10 min. Anti-rabbit secondary antibody Fluor 488 was diluted in 1:500 blocking solution, incubated for 4 h at room temperature, protected from light, washed twice with 10 mM PBS, 0.88% (wt.vol −1 ) NaCl, 0.1% (vol.vol −1 ) Tween 20, and 0.8% (wt/vol −1 ) BSA for 15 min each time, and then washed for 1 min with 10 mM PBS and blocked with glycerol ( Zheng et al, 2021 ). After Zeiss fluorescence microscopy imaging (Axio Imager D2), final editing was performed using Photoshop 2019.…”

OsMADS58 Stabilizes Gene Regulatory Circuits during Rice Stamen Development

“…Tapetum differentiation is regulated by many genes in rice [17,18]. Notably, mutants with aberrant MMC differentiation also fail to differentiate the tapetum properly, similar to that found in Arabidopsis [19][20][21][22]. It has therefore been suggested that tapetum differentiation is dependent on MMC differentiation [17,23].…”

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“…SPL/NZZ was suggested to be involved in auxin homeostasis 49 . A recent study showed that auxin distribution is associated with differentiation of the male germ cell PMC (pollen mother cell) 50 . Mutations in auxin biosynthesis genes TAA1 ( TRYPTOPHAN AMINOTRANSFERASE OF ARABIDOPSIS 1 ) and TAR2 ( TRYPTOPHAN AMINOTRANSFERASE RELATED 2 ) impair the PMC formation, whereas ectopic expression of SPL / NZZ partially rescues the PMC specification.…”