Genome-Wide Investigation of the NAC Gene Family and Its Potential Association with the Secondary Cell Wall in Moso Bamboo

Shan Shan,Yang Yang,Gao Gao,Xu Xu,Zhu Zhu

doi:10.3390/biom9100609

Abstract

NAC (NAM, ATAF, and CUC) transcription factors (TFs) are implicated in the transcriptional regulation of diverse processes and have been characterized in a number of plant species. However, NAC TFs are still not well understood in bamboo, especially their potential association with the secondary cell wall (SCW). Here, 94 PeNACs were identified and characterized in moso bamboo (Phyllostachys edulis). Based on their gene structures and conserved motifs, the PeNACs were divided into 11 groups according to their homologs in Arabidopsis. PeNACs were expressed variously in different tissues of moso bamboo, suggesting their functional diversity. Fifteen PeNACs associated with the SCW were selected for co-expression analysis and validation. It was predicted that 396 genes were co-expressed with the 15 PeNACs, in which 16 and 55 genes were involved in the lignin catabolic process and cellulose biosynthetic process respectively. As the degree of lignification in the growing bamboo shoots increased, all 15 PeNACs were upregulated with a trend of rising first and then decreasing except PeNAC37, which increased continuously. These results indicated that these PeNACs might play important roles in SCW biosynthesis and lignification in bamboo shoots. Seven of 15 PeNACs had been found positively co-expressed with seven PeMYBs, and they had similar expression patterns with those of the PeMYBs in bamboo shoots. The targeted sites of miR164 were found in 16 PeNACs, of which three PeNACs associated with SCW were validated to have an opposite expression trend to that of miR164 in growing bamboo shoots. In addition, three PeNACs were selected and verified to have self-activation activities. These results provide comprehensive information of the NAC gene family in moso bamboo, which will be helpful for further functional studies of PeNACs to reveal the molecular regulatory mechanisms of bamboo wood property.

Highlights

With the improvement in living standards, the demand for timber is rapidly growing, and timber supply is decreasing greatly, resulting in a need for alternative resources [1]
The purpose of this study is to gain a comprehensive understanding of NAC transcription factors (TFs) in moso bamboo, which will be helpful to reveal the molecular mechanisms of NAC TFs involved in the biosynthesis of secondary cell wall (SCW)
The characteristic parameters of the predicted proteins encoded by the PeNACs are shown in Table S1, including protein length, molecular weight, theoretical isoelectric point, and subcellular localization

Summary

Introduction

With the improvement in living standards, the demand for timber is rapidly growing, and timber supply is decreasing greatly, resulting in a need for alternative resources [1]. The development and utilization of bamboo resources can effectively alleviate the problems of restricted timber supply and decreasing timber quantity. Bamboo has a fast growth rate, high yield, and good material properties, such as high strength, good toughness, and high hardness compared with wood [2,3]. Bamboo is considered one of the important biomass energy sources. The formation and thickness of the secondary cell wall (SCW) play important roles during plant growth, producing a lignified texture and forming wood. The lignified SCW is the most environmentally friendly and cost-effective renewable resource

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Conclusion