AUTHOR=Liu Yang , Han Nannan , Wang Sheng , Chen Can , Lu Jie , Riaz Muhammad Waheed , Si Hongqi , Sun Genlou , Ma Chuanxi 

TITLE=Genome-Wide Identification of Triticum aestivum Xylanase Inhibitor Gene Family and Inhibitory Effects of XI-2 Subfamily Proteins on Fusarium graminearum GH11 Xylanase

JOURNAL=Frontiers in Plant Science

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2021.665501

DOI=10.3389/fpls.2021.665501

ISSN=1664-462X

ABSTRACT=<p><italic>Triticum aestivum</italic> xylanase inhibitor (<italic>TaXI</italic>) gene plays an important role in plant defense. Recently, <italic>TaXI–III</italic> inhibitor has been shown to play a dual role in wheat resistance to <italic>Fusarium graminearum</italic> infection. Thus, identifying the members of the <italic>TaXI</italic> gene family and clarifying its role in wheat resistance to stresses are essential for wheat resistance breeding. However, to date, no comprehensive research on <italic>TaXIs</italic> in wheat (<italic>Triticum aestivum L.</italic>) has been conducted. In this study, a total of 277 <italic>TaXI</italic> genes, including six genes that we cloned, were identified from the recently released wheat genome database (IWGSC RefSeq v1.1), which were unevenly located on 21 chromosomes of wheat. Phylogenetic analysis divided these genes into six subfamilies, all the six genes we cloned belonged to <italic>XI-2</italic> subfamily. The exon/intron structure of most <italic>TaXI</italic> genes and the conserved motifs of proteins in the same subfamily are similar. The <italic>TaXI</italic> gene family contains 92 homologous gene pairs or clusters, 63 and 193 genes were identified as tandem replication and segmentally duplicated genes, respectively. Analysis of the <italic>cis-</italic>acting elements in the promoter of <italic>TaXI</italic> genes showed that they are involved in wheat growth, hormone-mediated signal transduction, and response to biotic and abiotic stresses. RNA-seq data analysis revealed that <italic>TaXI</italic> genes exhibited expression preference or specificity in different organs and developmental stages, as well as in diverse stress responses, which can be regulated or induced by a variety of plant hormones and stresses. In addition, the qRT-PCR data and heterologous expression analysis of six <italic>TaXI</italic> genes revealed that the genes of <italic>XI-2</italic> subfamily have double inhibitory effect on GH11 xylanase of <italic>F. graminearum</italic>, suggesting their potential important roles in wheat resistance to <italic>F. graminearum</italic> infection. The outcomes of this study not only enhance our understanding of the <italic>TaXI</italic> gene family in wheat, but also help us to screen more candidate genes for further exploring resistance mechanism in wheat.</p>