Identification and expression analysis of TALE superfamily genes explore their key roles in response to abiotic stress in Brassica napus.

Background: The three-amino-acid-loop-extension (TALE) superfamily genes are broadly present in plants and play important roles in plant growth, development, and abiotic stress responses. So far, the TALE family in B.napus have not been systematically studied, especially their potential roles in response to abiotic stress.

Results: In this study, we identified 74 TALE family genes distributed on 19 chromosomes in the B. napus genome using bioinformatics methods. Phylogenetic analysis divided the BnTALE superfamily into two subfamilies, the BEL1-like (BLH/BELL homeodomain) and the KNOX (KNOTTED-like homeodomain) subfamilies. Moreover, the KNOX subfamily could be further categorized into three clades (KNOX Class I, KNOX Class II, and KNOX Class III). BnTALE members in the same subclass or branch of the phylogenetic tree generally showed similar gene structures and conserved domain compositions, which may indicate that they have similar biological functions. The BnTALE promoter regions contained many hormone-related elements and stress response elements. Duplication events identification analysis showed that WGD/segmental duplications were the main drivers of amplification during the evolution of TALE genes, and most of the duplicated BnTALE genes underwent purifying selection pressures during evolution. Potential protein interaction network analysis showed that a total of 12,615 proteins might interact with TALE proteins in B. napus. RNA-seq and qRT-PCR analyses showed that the expression of BnTALE was tissue-differentiated and can be induced by abiotic stresses such as dehydration, cold, and NaCl stress. In addition, weighted gene co-expression network analysis (WGCNA) identified four co-expression modules containing the most BnTALE genes, which would be notably related to dehydration and cold stresses.

Conclusions: Our study paves the way for future gene functional research of BnTALE and facilitate their applications in the genetic improvement of B. napus in response to abiotic stresses.