Arabidopsis GenesAS1,AS2, andJAGNegatively Regulate Boundary-Specifying Genes to Promote Sepal and Petal Development

Abstract

Boundary formation is crucial for organ development in multicellular eukaryotes. In higher plants, boundaries that separate the organ primordia from their surroundings have relatively low rates of cell proliferation. This cellular feature is regulated by the actions of certain boundary-specifying genes, whose ectopic expression in organs can cause inhibition of organ growth. Here, we show that the Arabidopsis thaliana ASYMMETRIC LEAVES1 and 2 (AS1 and AS2) and JAGGED (JAG) genes function in the sepal and petal primordia to repress boundary-specifying genes for normal development of the organs. Loss-of-function as1 jag and as2 jag double mutants produced extremely tiny sepals and petals. Analysis of a cell-cycle marker HISTONE4 revealed that cell division in sepal primordia of the double mutant was inhibited. Moreover, these abnormal sepals and petals exhibited ectopic overexpression of the boundary-specifying genes PETAL LOSS (PTL) and CUP-SHAPED COTYLEDONS1 and 2 (CUC1 and CUC2). Loss of PTL or CUC1 and CUC2 functions in the as1 jag background could partially rescue the tiny sepal and petal phenotypes, supporting the model that the tiny sepal/petal phenotypes are caused, at least in part, by ectopic expression of boundary-specifying genes. Together, our data reveal a previously unrecognized fundamental regulation by which AS1, AS2, and JAG act to define sepal and petal from their boundaries.

TCP Transcription Factors Regulate the Activities of ASYMMETRIC LEAVES1 and miR164, as Well as the Auxin Response, during Differentiation of Leaves inArabidopsis

“…The cooperative regulation of the expression of CUC genes appeared to induce morphological changes at the leaf margins and raised the level of expression of the KNAT1 gene ( Figure 7B). These results are consistent with reports of an antagonistic pathway involving AS1 and CUC genes that leads to the formation of the SAM and the development of floral organs (Hibara et al, 2003;Xu et al, 2008). By contrast, as1 did not affect the level of expression of TCP3 ( Figure 7C), indicating that the expression of TCP3 is not controlled by AS1.…”

Arabidopsis JAGGED LATERAL ORGANS Acts with ASYMMETRIC LEAVES2 to Coordinate KNOX and PIN Expression in Shoot and Root Meristems

“…LBD31 expression is first detectable at sites of organ initiation and later in meristem-to-organ boundaries. This expression pattern overlaps with that of JLO, AS2, and AS1 during early organ development and later with that of JLO in the boundary (Borghi et al, 2007;Iwakawa et al, 2007;Xu et al, 2008;Jun et al, 2010). Whether higher order complexes with LBD31 are formed has not been analyzed so far.…”

Members of the LATERAL ORGAN BOUNDARIES DOMAIN Transcription Factor Family Are Involved in the Regulation of Secondary Growth inPopulus

“…One of the founding members of the family, AS2/LBD6, was shown to regulate xylem/phloem specification in leaves (Lin et al, 2003;Xu et al, 2003;Zhu et al, 2008). Plants overexpressing AS2 formed adaxialized vascular bundles with xylem surrounding the phloem tissue (Lin et al, 2003;Xu et al, 2003Xu et al, , 2008. The observed effect on vascular development was likely mediated via a negative feedback loop with the abaxial regulator KANADI1 .…”