Analysis of the Arabidopsis Shoot Meristem Transcriptome during Floral Transition Identifies Distinct Regulatory Patterns and a Leucine-Rich Repeat Protein That Promotes Flowering

Abstract

Flowering of Arabidopsis thaliana is induced by exposure to long days (LDs). During this process, the shoot apical meristem is converted to an inflorescence meristem that forms flowers, and this transition is maintained even if plants are returned to short days (SDs). We show that exposure to five LDs is sufficient to commit the meristem of SD-grown plants to flower as if they were exposed to continuous LDs. The MADS box proteins SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1 (SOC1) and FRUITFULL (FUL) play essential roles in this commitment process and in the induction of flowering downstream of the transmissible FLOWERING LOCUS T (FT) signal. We exploited laser microdissection and Solexa sequencing to identify 202 genes whose transcripts increase in the meristem during floral commitment. Expression of six of these transcripts was tested in different mutants, allowing them to be assigned to FT-dependent or FT-independent pathways. Most, but not all, of those dependent on FT and its paralog TWIN SISTER OF FT (TSF) also relied on SOC1 and FUL. However, this dependency on FT and TSF or SOC1 and FUL was often bypassed in the presence of the short vegetative phase mutation. FLOR1, which encodes a leucine-rich repeat protein, was induced in the early inflorescence meristem, and flor1 mutations delayed flowering. Our data contribute to the definition of LD-dependent pathways downstream and in parallel to FT.

SWP73 Subunits of Arabidopsis SWI/SNF Chromatin Remodeling Complexes Play Distinct Roles in Leaf and Flower Development

“…Posthybridization washes were performed in 0.13 SSC (13 SSC is 0.15 M NaCl and 0.015 M sodium citrate). Previously described probes were employed for AGL24 (Torti et al, 2012) and AP3 (Zhao et al, 2007). For AP1, the template for probes to detect spatial transcript patterns were PCR amplified from cDNA using specific primer pairs (Supplemental Data Set 2) that amplify part of the cDNA with T7 RNA polymerase binding sites attached to the reverse primers.…”

Two Arabidopsis Loci Encode Novel Eukaryotic Initiation Factor 4E Isoforms That Are Functionally Distinct from the Conserved Plant Eukaryotic Initiation Factor 4E

“…However, RNA-Seq data can distinguish between the two genes and indicate that in flower tissue (Jiao and Meyerowitz, 2010;Niederhuth et al, 2013), shoot apical meristem (Torti et al, 2012), developing embryos (Nodine and Bartel, 2012), and the central cell of the female gamete (Schmid et al, 2012), EIF4E1B mRNA is expressed and associates with polysomes in flowers (Jiao and Meyerowitz, 2010); however, EIF4E1C mRNA was at much lower to undetectable levels in these tissues. In an analysis of 80 genomes released by the 1001 Genomes Project, EIF4E1C was predicted to be spontaneously deleted in 12 strains, suggesting that it is likely not providing any advantage to promote its retention in the genome .…”

Inflorescence Meristem Identity in Rice Is Specified by Overlapping Functions of Three AP1/FUL-Like MADS Box Genes and PAP2, a SEPALLATA MADS Box Gene

“…The conversion from the vegetative SAM to the IM is less well understood at the molecular level than events such as flowering time control, floral meristem specification, and flower development. Several genes show a dramatic change in their expression patterns in the meristem at phase transition (Cardon et al, 1997;Hempel et al, 1997;Lee et al, 2000;Samach et al, 2000;Torti et al, 2012). This reflects a global change in meristem gene expression that is associated with the establishment of IM identity (Schmid et al, 2003;Park et al, 2012).…”