Auxin response cell-autonomously controls ground tissue initiation in the early Arabidopsis embryo

Abstract

Significance Higher plants are built from three major tissue types: epidermis, ground tissue, and vascular tissue. Each of these differentiates into several functionally distinct cell types. Although identity switches for the different cell types within the major three tissues have been identified, mechanisms that trigger the initiation of the three tissues themselves have remained obscure. Auxin response, in particular the auxin-dependent transcription factor MONOPTEROS (MP), plays a critical role in Arabidopsis embryonic root initiation. In our study, we identify a set of embryonic MP target genes and show that MP acts as a very first regulator of ground tissue initiation. Moreover, our data provide a framework for the simultaneous formation of multiple cell types by the same transcriptional regulator.

Rice microtubule‐associated protein IQ67‐DOMAIN14 regulates grain shape by modulating microtubule cytoskeleton dynamics

“…Considering that the Arabidopsis AtIQD15‐18 subclade, acting downstream of the AUXIN RESPONSE FACTOR5/MONOPTEROS (ARF5/MP) transcription factor (Möller et al, ), is represented by a single OsIQD14 ortholog in rice (Abel et al , ), we analysed its expression pattern using the transcript digital gene chip. We found OsIQD14 to be highly expressed in inflorescences, pistils and spikelet hull tissues (Figure S1a), indicating that OsIQD14 may have potential roles in grain size regulation.…”

“…Young spikelet hulls and anthers showed a strong GUS signal (Figure b‐d), indicating that OsIQD14 may play a role during rice spikelet hull development. As some of the Arabidopsis orthologs were reported to be auxin‐inducible (Möller et al , ), we analysed OsIQD14 transcript levels upon exogenous auxin treatment. qRT‐PCR analysis confirmed that OsIQD14 transcripts were quickly induced upon auxin (indole 3‐acetic acid, IAA) treatment (Figure e), suggesting that OsIQD14 may also be transcriptionally regulated by ARFs in rice.…”

“…Auxin has been suggested to influence MT dynamics, but the mechanism is largely unknown (Chen et al , ). Recent studies showed that auxin‐mediated embryonic root formation may involve IQD proteins (Möller et al , ). OsIQD14 is the closest homolog of Arabidopsis AtIQD15‐18 subclade, some of which are transcriptionally regulated by the AUXIN RESPONSE FACTOR5/MONOPTEROS (ARF5/MP) transcription factor (Möller et al , ).…”

“…Recent studies showed that auxin‐mediated embryonic root formation may involve IQD proteins (Möller et al , ). OsIQD14 is the closest homolog of Arabidopsis AtIQD15‐18 subclade, some of which are transcriptionally regulated by the AUXIN RESPONSE FACTOR5/MONOPTEROS (ARF5/MP) transcription factor (Möller et al , ). The expression of OsIQD14 in rice was also induced by auxin, suggesting that rice and Arabidopsis IQDs may share a conserved upstream transcriptional regulatory mechanism.…”

Initiation and regulation of vascular tissue identity in theArabidopsisembryo

“…Conversely, lack of the AUXIN RESPONSE FACTOR5/MONOPTEROS (MP) transcription factor causes impaired vascular development in the Arabidopsis embryo, seedling, leaf and stem (Berleth and Jürgens, 1993;Hamann et al, 1999;Hardtke and Berleth, 1998;Mayer et al, 1991). Indeed, MP controls a variety of vascular-specific genes and pathways (De Rybel et al, 2013;Donner et al, 2009;Möller et al, 2017;Schlereth et al, 2010;Yoshida et al, 2019). However, all reported perturbations of auxin activity (synthesis, transport, response) that affect vascular development also affect a range of other processes (Bennett et al, 1996;Cheng et al, 2006;Marchant, 1999;van den Berg and ten Tusscher, 2017) .…”