Characterization of genes in the ASYMMETRIC LEAVES2/LATERAL ORGAN BOUNDARIES (AS2/LOB) family in Arabidopsis thaliana, and functional and molecular comparisons between AS2 and other family members

Abstract

The ASYMMETRIC LEAVES2 (AS2) gene is required for the generation of the flat and symmetrical shape of the leaf lamina in Arabidopsis. AS2 encodes a plant-specific protein with an AS2/LATERAL ORGAN BOUNDARIES (AS2/LOB) domain that includes a cysteine repeat, a conserved single glycine residue and a leucine-zipper-like sequence in its amino-terminal half. The Arabidopsis genome contains 42 genes, including AS2, that encode proteins with an AS2/LOB domain in their amino-terminal halves, and these genes constitute the AS2/LOB gene family. In the present study, we cloned and characterized cDNAs that covered the putative coding regions of all members of this family, and investigated patterns of transcription systematically in Arabidopsis plants. Comparisons among amino acid sequences that had been deduced from the cloned cDNAs revealed eight groups of genes, with two or three members each, and high degrees of identity among entire amino acid sequences, suggesting that some members of the AS2/LOB family might have redundant function(s). Moreover, no member of the family exhibited significant similarity, in terms of the deduced amino acid sequence of the carboxy-terminal half, to AS2. Results of domain swapping between AS2 and other members of the family showed that the AS2/LOB domain of AS2 cannot be functionally replaced by those of other members of the family, and that only a few dissimilarities among respective amino acid residues of the AS2/LOB domain of AS2 and those of other members are important for the specific functions of AS2.

The Lateral Organ Boundaries Domain Transcription Factor LBD20 Functions in Fusarium Wilt Susceptibility and Jasmonate Signaling in Arabidopsis

“…Five other LBD genes display similar or root-specific expression patterns like LBD20, with two of these, LBD14 and LBD33, the closest phylogenetically related to LBD20 (Shuai et al, 2002;Matsumura et al, 2009). This suggests subgroups of LBD proteins may have unique roles in roots.…”

“…This domain also determines the unique role of each LBD protein with LOB domains from other members unable to functionally replace each other (Matsumura et al, 2009;Majer and Hochholdinger, 2011). The LOB domain contains a Cys repeat (C motif), a conserved Gly residue, and a Leuzipper-like motif.…”

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

“…expressed in young lateral roots and LBD29 in lateral root primordia, while LBD18 was more ubiquitously detected in most organs [19,28,34]. To investigate the temporal and spatial expression of LBD genes during callus induction, we chose LBD16 and LBD18 as the representatives and carefully examined their expression patterns during callus induction using ProLBD16:GUS and ProLBD18:EGFP:GUS transgenic seedlings.…”

LBD18/ASL20Regulates Lateral Root Formation in Combination withLBD16/ASL18Downstream ofARF7andARF19in Arabidopsis

“…The results of misexpression experiments indicate that during postembryonic development, JLO function is required for the initiation of plant lateral organs. A recent study showed that the LOB domain of AS2 cannot be functionally replaced by those of other members of the LOB family, indicating that dissimilar amino acid residues in the LOB domains are important for characteristic functions of the family members (Matsumura et al, 2009). …”