The ERECTA, CLAVATA and class III HD-ZIP Pathways Display Synergistic Interactions in Regulating Floral Meristem Activities

Abstract

In angiosperms, the production of flowers marks the beginning of the reproductive phase. At the emergence of flower primordia on the flanks of the inflorescence meristem, the WUSCHEL (WUS) gene, which encodes a homeodomain transcription factor starts to be expressed and establishes de novo stem cell population, founder of the floral meristem (FM). Similarly to the shoot apical meristem a precise spatial and temporal expression pattern of WUS is required and maintained through strict regulation by multiple regulatory inputs to maintain stem cell homeostasis. However, following the formation of a genetically determined fixed number of floral organs, this homeostasis is shifted towards organogenesis and the FM is terminated. In here we performed a genetic study to test how a reduction in ERECTA, CLAVATA and class III HD-ZIP pathways affects floral meristem activity and flower development. We revealed strong synergistic phenotypes of extra flower number, supernumerary whorls, total loss of determinacy and extreme enlargement of the meristem as compared to any double mutant combination indicating that the three pathways, CLV3, ER and HD-ZIPIII distinctively regulate meristem activity and that they act in parallel. Our findings yield several new insights into stem cell-driven development. We demonstrate the crucial requirement for coupling floral meristem termination with carpel formation to ensure successful reproduction in plants. We also show how regulation of meristem size and alternation in spatial structure of the meristem serve as a mechanism to determine flower organogenesis. We propose that the loss of FM determinacy due to the reduction in CLV3, ER and HD-ZIPIII activity is genetically separable from the AGAMOUS core mechanism of meristem termination.

A high-quality genome provides insights into the new taxonomic status and genomic characteristics of Cladopus chinensis (Podostemaceae)

“…Several studies have focused on the establishment of the SAM, including the auxin-related gene activities, transcription factors and morphological characteristics involved [9][10][11][12][13] . A low auxin level contributes to the initial establishment of the apical-basal axis that extends to form the apical meristems of the shoots 9 .…”

“…MP expression is relatively weak in auxin-deficient conditions 10 . WUSCHEL (WUS) is a homeodomain transcription factor whose expression establishes a de novo stem cell population 11 . SHOOT MERISTEMLESS (STM) encodes a MEINOX/three-amino acid loop extension (TALE)-HDtype transcription factor required for the initiation and maintenance of the SAM 12 .…”

Characterization of wheat homeodomain-leucine zipper family genes and functional analysis of TaHDZ5-6A in drought tolerance in transgenic Arabidopsis

“…Clade α corresponds to the REV clade described in previous studies [54], which are orthologs of the wheat TaHDZ25-1A/B/D and TaHDZ26-4B/D genes. Clade β includes Arabidopsis ATHB8 [17] and ATHB15/CNA [19], which are the orthologs of wheat TaHDZ24-3A/B/D, and clade γ contains PHB and PHV [55,56], which are the orthologs of wheat TaHDZ27-5A/B/D and TaHDZ28-5A/B/D. The HD-Zip IV subfamily also consists of six subclades, designated α, β, γ, δ, ε, and ζ ( To better understand the roles of the wheat HD-Zip genes during the life cycle of wheat, we performed an expression analysis of publicly-available RNA-seq data in 10 organs/tissues at different developmental stages.…”

“…ATHB8 and ATHB15 are thought to direct vascular development [17,18]. CLV3 has been shown to interact with HD-Zip III members to regulate floral meristem activities [19], and KANADI interacts with HD-Zip III genes to control lateral root development [20].…”

CORONA, PHABULOSA and PHAVOLUTA collaborate with BELL 1 to confine WUSCHEL expression to the nucellus in Arabidopsis ovules

“…Class III homeodomain leucine zipper (HD-ZIPIII) genes establish the identity of the adaxial tissue of lateral organs (Emery et al, 2003;McConnell et al, 2001), as well as regulating WUS expression in shoot and floral apices in cooperation with CLAVATA3 or ERECTA (ER) homologs (Green et al, 2005;Landau et al, 2015;Lee and Clark, 2015;Mandel et al, 2014). In ovules, HD-ZIPIII genes are involved in the development of the integuments; thus, in most ovules of loss-of-function HD-ZIPIII gene mutants [i.e.…”