The CUP-SHAPED COTYLEDON3 Gene Is Required for Boundary and Shoot Meristem Formation in Arabidopsis

Abstract

From an enhancer trap screen for genes expressed in Arabidopsis embryos, we identified a gene expressed from the octant stage onward in the boundary between the two presumptive cotyledons and in a variety of postembryonic organ and meristem boundaries. This gene, CUP-SHAPED COTYLEDON3 ( CUC3 ), encodes a putative NAC-domain transcription factor that is homologous with CUC1 and CUC2. Analysis of a CUC3 hypomorph and a putative cuc3 null mutant indicates that CUC3 function is partially redundant with that of CUC1 and CUC2 in the establishment of the cotyledon boundary and the shoot meristem, thus revealing an even higher degree of redundancy in this class of genes than was thought previously. The CUC3 expression pattern, the cuc3 phenotypes, and CUC3 expression in a series of shoot meristem mutants and transgenes suggest a primary role for CUC 3 in the establishment of boundaries that contain cells with low proliferation and/or differentiation rates. The CUC -mediated establishment of such boundaries may be essential for the initiation of shoot meristems.

Coordination of apical and basal embryo development revealed by tissue-specific GNOM functions

“…5D), which has never been observed for gnom, demonstrating the reconstituted activity of the shoot apical meristem. The fused apical phenotype was reminiscent of cuc1 cuc2 double mutants, which are impaired in organ boundary formation (Aida et al, 2002;Vroemen et al, 2003). Indeed, CUC2 localization was disrupted in gnom (not shown).…”

Divide and conquer: development and cell cycle genes in plant transformation

“…In Arabidopsis, the CUC genes CUC1 and CUC2 act upstream of the STM (SHOOTMERISTEM-LESS) gene, whereas the double mutant cuc1 cuc2 results in an absence of meristem [49]. CUC proteins transactivate genes involved in SAM formation and organ separation, where CUC3 encodes a major determinant of boundary specification, and CUC2 is essential for shoot apical meristem initiation [12]. Both CUC1 and CUC2 are post-translationally regulated by micro RNA miR164 [50,51].…”

“…The processes of plant transformation and regeneration from a transgenic cell can stall at several key points, including: (1) the acquisition of a stem-cell-like state in cells as they re-enter the cell cycle [7]; (2) progression between the G1 and S phases of the cycle [8,9] (Box 1); and (3) the differentiation of the transformed cell into a new embryo or meristem [10][11][12][13]. In this manuscript, we consider transformation to be the recovery of cells expressing a foreign gene for use as a selectable marker, and regeneration to be the organogenesis or embryogenesis from the genetically transformed cells.…”

The Arabidopsis PRC1-like ring-finger proteins are necessary for repression of embryonic traits during vegetative growth

“…Consistent with our previous findings [7], the key SAM-regulatory genes (STM, BP/ KNAT1, KNAT2 and KNAT6) encoding Class I KNOX transcription factors are upregulated by 2-to 6-fold in the mutant. The NAC-domain transcription factor genes CUC1, CUC2 and CUC3, which are required for organ boundary establishment and SAM initiation [13], are upregulated by 3-to 15-fold in the double mutant ( Figure 3A). While the homeodomain transcription factor gene WUS and its homologue WOX2, which are essential for SAM organizing center activity and apical embryo-axis cell fate [14,15], are only slightly upregulated, WOX5 and WOX8, which are crucial for RAM function and basal embryo-axis cell fate termination [15], are upregulated by more than 5-fold in the mutant ( Figure 3A).…”