The ASYMMETRIC LEAVES2 Gene of Arabidopsis thaliana, Required for Formation of a Symmetric Flat Leaf Lamina, Encodes a Member of a Novel Family of Proteins Characterized by Cysteine Repeats and a Leucine Zipper

Abstract

The ASYMMETRIC LEAVES2 (AS2) gene of Arabidopsis thaliana is involved in the establishment of the leaf venation system, which includes the prominent midvein, as well as in the development of a symmetric lamina. The gene product also represses the expression of class 1 knox homeobox genes in leaves. We have characterized the AS2 gene, which appears to encode a novel protein with cysteine repeats (designated the C-motif) and a leucine-zipper-like sequence in the amino-terminal half of the primary sequence. The Arabidopsis genome contains 42 putative genes that potentially encode proteins with conserved amino acid sequences that include the C-motif and the leucine-zipper-like sequence in the amino-terminal half. Thus, the AS2 protein belongs to a novel family of proteins that we have designated the AS2 family. Members of this family except AS2 also have been designated ASLs (AS2-like proteins). Transcripts of AS2 were detected mainly in adaxial domains of cotyledonary primordia. Green fluorescent protein-fused AS2 was concentrated in plant cell nuclei. Overexpression of AS2 cDNA in transgenic Arabidopsis plants resulted in upwardly curled leaves, which differed markedly from the downwardly curled leaves generated by loss-of-function mutation of AS2. Our results suggest that AS2 functions in the transcription of a certain gene(s) in plant nuclei and thereby controls the formation of a symmetric flat leaf lamina and the establishment of a prominent midvein and other patterns of venation.

LATERAL ORGAN BOUNDARIES DOMAIN transcription factors direct callus formation in Arabidopsis regeneration

“…Although the precise molecular mechanism remains unclear, our study clearly demonstrates that LBD transcription factors are key regulators in directing callus formation in a typical in vitro plant regeneration system. In addition, since the LBD family comprises a large number of members in plant genomes, it is likely that other close LBD homologues may also have some effect on callus formation, which might explain why transgenic plants overexpressing Arabidopsis LBD6/AS2 or poplar LBD1 displayed a slightly enhanced callus-forming phenotype [18,26].…”

“…The LBD family comprises 43 members in Arabidopsis, 35 in rice and 57 in poplar [18][19][20][21]. Functional characterization of several LBD members revealed that LBD genes play critical roles in defining lateral organ boundaries and regulating many aspects of plant development, including root, leaf, inflorescence and embryo development.…”

CUC1 gene activates the expression of SAM‐related genes to induce adventitious shoot formation

“…AS1 encodes a MYB domain transcription factor related to Antirrhinum PHANTASTICA and maize ROUGH SHEATH2 (Byrne et al, 2000;Schneeberger et al, 1998;Sun et al, 2002;Waites et al, 1998). AS2 encodes a nuclear-localized protein that contains cysteine repeats and a leucine-zipperlike motif (Iwakawa et al, 2002). The as1 and as2 mutations suppress the embryonic and vegetative phenotype of the stm mutant, as as1 stm and as2 stm double mutants form a SAM (Byrne et al, 2000(Byrne et al, , 2002.…”

BLADE-ON-PETIOLE–Dependent Signaling Controls Leaf and Floral Patterning in Arabidopsis

“…; Semiarti et al, 2001;Sun et al, 2002), AS2, which encodes a LOB domain/Leu zipper transcription factor (Iwakawa et al, 2002;Lin et al, 2003), and BLADE-ON-PETIOLE1 (BOP1), recently shown to encode a NONEXPRESSOR OF PR GENES1 (NPR1)-like transcription factor (Ha et al, 2003(Ha et al, , 2004. AS1 and AS2 function in the same genetic pathway and bind to each other in yeast, suggesting that they are members of a complex (Byrne et al, 2002;Iwakawa et al, 2002;Lin et al, 2003;Xu et al, 2003).…”