MiR397b regulates both lignin content and seed number in Arabidopsis via modulating a laccase involved in lignin biosynthesis

Abstract

SummaryPlant laccase (LAC) enzymes belong to the blue copper oxidase family and polymerize monolignols into lignin. Recent studies have established the involvement of microRNAs in this process; however, physiological functions and regulation of plant laccases remain poorly understood. Here, we show that a laccase gene, LAC4, regulated by a microRNA, miR397b, controls both lignin biosynthesis and seed yield in Arabidopsis. In transgenic plants, overexpression of miR397b (OXmiR397b) reduced lignin deposition. The secondary wall thickness of vessels and the fibres was reduced in the OXmiR397b line, and both syringyl and guaiacyl subunits are decreased, leading to weakening of vascular tissues. In contrast, overexpression of miR397b-resistant laccase mRNA results in an opposite phenotype. Plants overexpressing miR397b develop more than two inflorescence shoots and have an increased silique number and silique length, resulting in higher seed numbers. In addition, enlarged seeds and more seeds are formed in these miR397b overexpression plants. The study suggests that miR397-mediated development via regulating laccase genes might be a common mechanism in flowering plants and that the modulation of laccase by miR397 may be potential for engineering plant biomass production with less lignin.

The pivotal role of small non-coding RNAs in the regulation of seed development

“…Down-regulation of the mir397 target gene OsLAC, encoding a laccase-like protein involved in brassinosteroid sensitivity, by overexpression of the miR397 has remarkable effects in the seeds including enlarged grain size, increased panicle branching, and up to 25% increase in overall grain yield (Zhang et al 2013a). Also Wang et al (2014) showed that overexpression of the Arabidopsis miR397b leads to an increased silique length and number of inflorescence shoots and siliques, resulting in a higher number of seeds. In addition, the plants showed a deregulation of another laccase gene, LAC4 gene, leading to a general weakening of the vascular tissues in Arabidopsis, caused by a reduction in lignin deposition and in the secondary wall thickness of vessels and fibres.…”

miRNAs and lncRNAs in reproductive development

“…miRNAs play crucial roles in a variety of plant biological processes including the developmental regulation of organs, and biotic and abiotic stress responses [3]. More importantly, recent studies have also revealed that miRNAs are regulators of crop yield and secondary cell wall formation [4,5], indicating their potential in modulating important agronomic traits. In addition to miRNAs, there are many lncRNAs in plant genomes.…”

MicroRNA858 Is a Potential Regulator of Phenylpropanoid Pathway and Plant Development

“…Studies also have revealed that miR397 regulates lignin biosynthesis by altering laccase expression in Arabidopsis and Populus spp. (Lu et al, 2013;Wang et al, 2014). It has been reported that the miR159, miR319, and miR828 families deregulate MYB transcription factors in apple (Malus domestica), tomato (Solanum lycopersicum), grape (Vitis vinifera), and Salvia miltiorrhiza (Xia et al, 2012;Rock, 2013;Li et al, 2014;Jia et al, 2015).…”