Genome-Wide Identification of Sorghum bicolor Laccases Reveals Potential Targets for Lignin Modification

Abstract

Laccase is a key enzyme in plant lignin biosynthesis as it catalyzes the final step of monolignols polymerization. Sweet sorghum [Sorghum bicolor (L.) Moench] is considered as an ideal feedstock for ethanol production, but lignin greatly limits the production efficiency. No comprehensive analysis on laccase has ever been conducted in S. bicolor, although it appears as the most promising target for engineering lignocellulosic feedstock. The aim of our work is to systematically characterize S. bicolor laccase gene family and to identify the lignin-specific candidates. A total of twenty-seven laccase candidates (SbLAC1-SbLAC27) were identified in S. bicolor. All SbLACs comprised the equivalent L1-L4 signature sequences and three typical Cu-oxidase domains, but exhibited diverse intron-exon patterns and relatively low sequence identity. They were divided into six groups by phylogenetic clustering, revealing potential distinct functions, while SbLAC5 was considered as the closest lignin-specific candidate. qRT-PCR analysis deciphered that SbLAC genes were expressed preferentially in roots and young internodes of sweet sorghum, and SbLAC5 showed high expression, adding the evidence that SbLAC5 was bona fide involved in lignin biosynthesis. Besides, high abundance of SbLAC6 transcripts was detected, correlating it a potential role in lignin biosynthesis. Diverse cis regulatory elements were recognized in SbLACs promoters, indicating putative interaction with transcription factors. Seven SbLACs were found to be potential targets of sbi-miRNAs. Moreover, putative phosphorylation sites in SbLAC sequences were identified. Our research adds to the knowledge for lignin profile modification in sweet sorghum.

Large scale genome-wide association study reveals that drought induced lodging in grain sorghum is associated with plant height and traits linked to carbon remobilisation

“…Twelve of the 21 genes involved in lignin biosynthesis (Bout and Vermerris 2003; Saballos et al 2009, 2012, Sattler et al 2009, 2017, Walker et al 2013, 2016, Jun et al 2017, 2018; Wang et al 2017) were located within genomic regions associated with lodging in this study (Fig. 2), representing a significant enrichment (χ 2 test, p value = 0.008).…”

“…Twelve of the 21 genes involved in lignin biosynthesis (Bout and Vermerris, 2003; Jun et al , 2017, 2018, Saballos et al , 2012, 2009, Sattler et al , 2009, 2017, Walker et al , 2013, 2016; Wang et al , 2017) were located within genomic regions associated with lodging in this study (Figure 2), representing a significant enrichment (χ 2 test, p value = 0.008). Lodging resistant sorghum generally have more lignification, both in the number of cells with lignified walls and in the degree of lignification in the epidermis, sub-epidermis, and vascular bundles (Schertz and Rosenow, 1977).…”

“…Brown vertical bars to the right of each chromosome marked as “LDG” represent the locations of QTL previously detected for lodging (Kebede et al , 2001; Murray et al , 2008; Srinivasa Reddy et al , 2008); the black bars indicate the location of a QTL previously reported for charcoal rot and/or Fusarium stalk rot (Srinivasa Reddy et al 2008; Adeyanju et al 2015). The location of genes in the lignin biosynthesis pathways that co-located with lodging QTL detected in this study are highlighted in green to the right of each chromosome, and those that did not co-locate with lodging QTL are highlighted in blue (Bout and Vermerris 2003; Saballos et al 2009, 2012, Sattler et al 2009, 2017, Walker et al 2013, 2016, Jun et al 2017, 2018; Wang et al 2017). The location of the recently cloned Dry gene is highlighted in red (Zhang et al 2018).…”

“…A limited number of genes for stem composition have been identified and functionally validated in sorghum. Based on phylogenetic relationships with functionally confirmed genes in sorghum and other species, predicted translational protein functions, enzymatic activity assay, and gene expression patterns, 21 candidate genes in the lignin biosynthesis pathways have been identified in sorghum (Bout and Vermerris 2003; Saballos et al 2009, 2012, Sattler et al 2009, 2017, Walker et al 2013, 2016, Jun et al 2017, 2018; Wang et al 2017). Additionally, the major morphological D gene, which changes the structure of the sorghum pith, was recently cloned (Zhang et al 2018).…”

Plant Responses to Pathogen Attack: Small RNAs in Focus

“…Even though the exact role of plantacyanins in plants is mysterious; however, they are supposed to be involved in stress responses cell-to-cell signaling and lignin production [ 173 , 174 ]. Similarly, laccases regulate varied tasks in plants, e.g., lignin synthesis, wound healing, iron acquirement, stress response, and cell wall structure maintenance and veracity [ 175 , 176 ]. Therefore, differential regulation of miR408 in wheat cultivars susceptible and resistant to Puccinia graminis f. sp.…”