DORNRÖSCHEN-LIKE expression marks Arabidopsis floral organ founder cells and precedes auxin response maxima

Abstract

Live imaging during floral development revealed that expression of the DORNRÖSCHEN-LIKE (DRNL) gene encoding an AP2-like transcription factor, marks all organ founder cells. Transcription precedes the perception of auxin response maxima as measured by the DR5 reporter and is unaffected in early organogenesis, by mutation of four canonical auxin response elements (AuxREs) in the DRNL promoter. DRNL expression identifies discrete modes of organ initiation in the four floral whorls, from individual or pairs of organ anlagen in the outer whorl of sepals to two morphogenetic fields pre-patterning petals and lateral stamens, or a ring-shaped field giving rise to the medial stamens before carpel primordia are specified. DRNL function only overlaps in the central stem cell zone with that of its paralogue, DORNRÖSCHEN (DRN). drnl mutants are affected in floral organ outgrowth, which functionally interplays with boundary specification as organ fusions are sensitized by loss of CUP-SHAPED COTYLEDON (CUC) gene activity, and synergistic interactions exist with mutants in local auxin biosynthesis and polar transport. DRNL apparently monitors and contributes to cellular decisions in the SAM and thus provides a novel molecular access to the interplay of founder cell specification, organ anlage and organogenesis in the SAM peripheral zone.

Coordination of auxin-triggered leaf initiation by tomato LEAFLESS

“…But how auxin, a broad-acting hormone, specifies primordia cells, has remained an enigma. The results of this and previous studies (3,5,21) provide a framework (Fig. 5M) for understanding the specification process.…”

“…4D), these plants did not support a viable SAM throughout their lives, and thus organ initiation could not be assessed. Notably, when the weaker allele drnl-1 is used to generate double-mutant drn drnl plants, their phenotype is much weaker and most plants have rather normal shoots (19,21). Both tomato lfs and Arabidopsis drn drnl seeds had a short shelf life, and their germination rate decreased with time, leading to non-Mendelian segregation ratios.…”

SUPERMAN prevents class B gene expression and promotes stem cell termination in the fourth whorl of Arabidopsis thaliana flowers

“…At that stage, DRNL is also expressed in two foci in whorl 4, which correspond to the sites of carpel initiation, and in two narrow arcs of cells connecting these foci (Fig. S3 B and C) (14). SUP and DRNL expression partially overlap in stamen primordia in whorl 3 ( Fig.…”

“…S3 A and B) (14). In particular, DRNL expression in whorl 3 forms a ring at early stage 4 that is reminiscent of AP3 and SUP expression patterns, before being restricted to foci at the sites of stamen initiation at stage 5 ( Fig.…”

Arabidopsis ENHANCER OF SHOOT REGENERATION 2 and PINOID are involved in in vitro shoot regeneration

“…Frequencies of abnormal cotyledons (one cotyledon or two fused cotyledons in Table 1) emerging on progenies from the parental genotype esr2-2 (2.75%) were higher than frequencies on progenies from the parental genotype drnl-1 (0.71%; Chandler et al 2011a), suggesting that esr2-2 is a stronger allele than drnl-1. Our pid plants were sterile, whereas pid-2 plants appeared to be partially fertile (Chandler et al 2011b), suggesting that pid is a stronger allele than pid-2. Our double mutants had more severe phenotypes than the drnl-1 pid-2 double mutants did, probably because we used stronger alleles of both mutations than drnl-1 and pid-2 generated by Chandler and colleagues (2011a, b).…”