Abstract
The β-1,3-glucanase gene family is involved in a wide range of plant developmental processes as well as pathogen defense mechanisms. Comprehensive analyses of β-1,3-glucanase genes (GLUs) have not been reported in cotton. Here, we identified 67, 68, 130 and 158 GLUs in four sequenced cotton species, G. raimondii (D5), G. arboreum (A2), G. hirsutum acc. TM-1 (AD1), and G. barbadense acc. 3–79 (AD2), respectively. Cotton GLUs can be classified into the eight subfamilies (A–H), and their protein domain architecture and intron/exon structure are relatively conserved within each subfamily. Sixty-seven GLUs in G. raimondii were anchored onto 13 chromosomes, with 27 genes involved in segmental duplications, and 13 in tandem duplications. Expression patterns showed highly developmental and spatial regulation of GLUs in TM-1. In particular, the expression of individual member of GLUs in subfamily E was limited to roots, leaves, floral organs or fibers. Members of subfamily E also showed more protein evolution and subgenome expression bias compared with members of other subfamilies. We clarified that GLU42 and GLU43 in subfamily E were preferentially expressed in root and leaf tissues and significantly upregulated after Verticillium dahliae inoculation. Silencing of GLU42 and GLU43 significantly increased the susceptibility of cotton to V. dahliae.
Highlights
The hydrolysis of 1,3-β-D-glucosidic linkages in β-1,3-glucans is catalyzed by the enzymes of β-1,3-glucanases (E.C. 3.2.1.39), which are widely found in bacteria, fungi, viruses[1,2] and various plant species, including Arabidopsis[3], rice[4], tobacco[5] and soybean6. β-1,3-Glucanase genes (GLUs) have formed complex and diverse gene families in plants, where they play important roles in a wide range of physiological and developmental processes[3]
Specific focus was placed on the GLUs in subfamily E and virus-induced gene silencing (VIGS) analysis confirmed that silencing of the two GLUs in subfamily E significantly increased the susceptibility of cotton to V. dahlia
We identified 68 GLUs in G. arboreum. As these had an orthologous relationship to the GLUs in G. raimondii, the 67 GLUs in G. arboreum were named GaGLU1-67, corresponding to GrGLU1-67
Summary
The hydrolysis of 1,3-β-D-glucosidic linkages in β-1,3-glucans is catalyzed by the enzymes of β-1,3-glucanases (E.C. 3.2.1.39), which are widely found in bacteria, fungi, viruses[1,2] and various plant species, including Arabidopsis[3], rice[4], tobacco[5] and soybean6. β-1,3-Glucanase genes (GLUs) have formed complex and diverse gene families in plants, where they play important roles in a wide range of physiological and developmental processes[3]. Β-1,3-Glucanase genes (GLUs) have formed complex and diverse gene families in plants, where they play important roles in a wide range of physiological and developmental processes[3]. Β-1,3-Glucanases have been proposed to play important roles in physiological and developmental processes, as well as in the response of plants to microbial pathogens, and show great functional diversity between the members of this large gene family[7]. The publically available genomic information from four sequenced cotton species, G. raimondii[16], G. arboreum[17], G. hirsutum[18] and G. barbadense[19], provides us with a data source to identify candidate GLUs at a genome-wide level in Gossypium, and to mine key genes for the genetic improvement of yield and fiber quality, as well as disease resistance. Our study provides a basis for systematically elucidating the evolutionary and functional characteristics of GLUs in cotton, for the effective clarification of the precise biological roles of GLUs and their utilization in future cotton-breeding programs
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