Temporal Gene Expression in Apical Culms Shows Early Changes in Cell Wall Biosynthesis Genes in Sugarcane.

Guilherme Kenichi Hosaka,Anete Pereira De Souza,Fernanda Zatti Barreto,Nicholas James Provart,Danilo Augusto Sforça,Fernando Henrique Correr,Monalisa Sampaio Carneiro,Carla Cristina Da Silva,Thiago Willian Almeida Balsalobre,Gabriel Rodrigues Alves Margarido,Asher Pasha

doi:10.3389/fpls.2021.736797

Abstract

Multiple genes in sugarcane control sucrose accumulation and the biosynthesis of cell wall components; however, it is unclear how these genes are expressed in its apical culms. To better understand this process, we sequenced mRNA from +1 stem internodes collected from four genotypes with different concentrations of soluble solids. Culms were collected at four different time points, ranging from six to 12-month-old plants. Here we show differentially expressed genes related to sucrose metabolism and cell wall biosynthesis, including genes encoding invertases, sucrose synthase and cellulose synthase. Our results showed increased expression of invertases in IN84-58, the genotype with lower sugar and higher fiber content, as well as delayed expression of secondary cell wall-related cellulose synthase for the other genotypes. Interestingly, genes involved with hormone metabolism were differentially expressed across time points in the three genotypes with higher soluble solids content. A similar result was observed for genes controlling maturation and transition to reproductive stages, possibly a result of selection against flowering in sugarcane breeding programs. These results indicate that carbon partitioning in apical culms of contrasting genotypes is mainly associated with differential cell wall biosynthesis, and may include early modifications for subsequent sucrose accumulation. Co-expression network analysis identified transcription factors related to growth and development, showing a probable time shift for carbon partitioning occurred in 10-month-old plants.

Highlights

Brazil is the main sugarcane producer in the world, followed by India, Thailand and China (Food and Agriculture Organization, 2021)
In this study we analyzed immature culms of four sugarcane genotypes contrasting in their soluble solids content, at four time points during the growing season ranging from 6- to 12-monthold plants
Our goal was to study gene expression changes in apical culms related to carbon partitioning, aiming to understand differences between genotypes contrasting in their sugar content

Summary

Introduction

Brazil is the main sugarcane producer in the world, followed by India, Thailand and China (Food and Agriculture Organization, 2021). Used commercial sugarcane genotypes are hybrids, mainly between the species Saccharum officinarum and Saccharum spontaneum The former was used because of its higher sugar content in its culms, and the latter for its robustness, resistance to diseases (Campos and Caligari, 2017) and abiotic stress tolerance (Zhang et al, 2018). Successive backcrossing with S. officinarum was used to increase sugar content yield, a process called “nobilization” (Piperidis et al, 2020). These noble canes exhibit lower fiber content, thicker culms and recalcitrant flowering when compared to S. spontaneum (Kaffka and Grantz, 2014). Modern sugarcane cultivars (Saccharum X officinarum) are aneuploid and autopolyploid, with a basic ploidy level of 10x to 12x (Piperidis and D’Hont, 2020), resulting in a total genome size of roughly 10 Gbp (D’Hont, 2005)

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