Abstract
The lateral organ boundaries domain (LBD) genes, as the plant-specific transcription factor family, play a crucial role in controlling plant architecture and stress tolerance. Although it has been thoroughly characterized in many species, the LBD family was not well studied in wheat. Here, the wheat LBD family was systematically investigated through an in silico genome-wide search method. A total of 90 wheat LBD genes (TaLBDs) were identified, which were classified into class I containing seven subfamilies, and class II containing two subfamilies. Exon–intron structure, conserved protein motif, and cis-regulatory elements analysis showed that the members in the same subfamily shared similar gene structure organizations, supporting the classification. Furthermore, the expression patterns of these TaLBDs in different types of tissues and under diverse stresses were identified through public RNA-seq data analysis, and the regulation networks of TaLBDs involved were predicted. Finally, the expression levels of 12 TaLBDs were validated by quantitative PCR (qPCR) analysis and the homoeologous genes showed differential expression. Additionally, the genetic diversity of TaLBDs in the landrace population showed slightly higher than that of the genetically improved germplasm population while obvious asymmetry at the subgenome level. This study not only provided the potential targets for further functional analysis but also contributed to better understand the roles of LBD genes in regulating development and stress tolerance in wheat and beyond.
Highlights
The lateral organ boundaries domain (LBD), called the AS2/LOB gene family, is one class of plant-specific transcription factors, which plays an important role in regulating lateral organ development, morphogenesis, and metabolism in plants (Majer and Hochholdinger, 2011)
A total of 90 putative LBD proteins were identified in the wheat genome, which represented the most abundant LBD family among plants, indicating that the LBD gene family expanded significantly in wheat (Tables 1, 2)
A total of 31, 29, and 29 LBD genes are non-randomly distributed in the wheat A, B, and D subgenomes, respectively, indicating that there was no significant difference in the LBD abundance at the subgenome level
Summary
The lateral organ boundaries domain (LBD), called the AS2/LOB gene family, is one class of plant-specific transcription factors, which plays an important role in regulating lateral organ development, morphogenesis, and metabolism in plants (Majer and Hochholdinger, 2011). LBD transcription factors are typically defined by an N-terminal LBD domain, which generally comprises a C-domain containing four highly conserved cysteine (C) residues in a CX2CX6CX3C zinc. Some LBD proteins possessed the glycine residue and leucine zipper-like motif LX6LX3LX6L (Shuai et al, 2002; Matsumura et al, 2009). Class I members usually contain four highly conserved cys residues in a CX2CX6CX3C motif, together with a leucine zipper-like motif (LX6LX3LX6L) that can form the coiled-coiled structure for protein interactions, while class II members have the conserved cys residues and leucine zipper-like domain that cannot form the coiled-coil structure (Landschaslz, 1998). The majority of LBD proteins belong to class I and widely participate in regulating plant development and signal transduction (Majer and Hochholdinger, 2011; Yu et al, 2020)
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