Biomass Accumulation and Cell Wall Structure of Rice Plants Overexpressing a Dirigent-Jacalin of Sugarcane (ShDJ) Under Varying Conditions of Water Availability

Larissa Mara Andrade,João Felipe Carlos De Oliveira Nebó,Juan Pablo Portilla Llerena,Maria Helena S Goldman,Antonio Figueira,Jorge Da Silva,Silvana Creste,Michael Santos Brito,Rafael Fávero Peixoto-Junior,Dilermando Perecin,Paula Macedo Nóbile,Paulo Mazzafera,Paulo Eduardo Ribeiro Marchiori,Thiago Romanos Benatti,Rafael Vasconcelos Ribeiro,Alexandre Palma Boer Martins,Samira Domingues Carlin,Caroline Fregonesi

doi:10.3389/fpls.2019.00065

Abstract

A sugarcane gene encoding a dirigent-jacalin, ShDJ, was induced under drought stress. To elucidate its biological function, we integrated a ShDJ-overexpression construction into the rice Nipponbare genome via Agrobacterium-mediated transformation. Two transgenic lines with a single copy gene in T0 were selected and evaluated in both the T1 and T4 generations. Transgenic lines had drastically improved survival rate under water deficit conditions, at rates close to 100%, while WT did not survive. Besides, transgenic lines had improved biomass production and higher tillering under water deficit conditions compared with WT plants. Reduced pectin and hemicellulose contents were observed in transgenic lines compared with wild-type plants under both well-watered and water deficit conditions, whereas cellulose content was unchanged in line #17 and reduced in line #29 under conditions of low water availability. Changes in lignin content under water deficit were only observed in line #17. However, improvements in saccharification were found in both transgenic lines along with changes in the expression of OsNTS1/2 and OsMYB58/63 secondary cell wall biosynthesis genes. ShDJ-overexpression up-regulated the expression of the OsbZIP23, OsGRAS23, OsP5CS, and OsLea3 genes in rice stems under well-watered conditions. Taken together, our data suggest that ShDJ has the potential for improving drought tolerance, plant biomass accumulation, and saccharification efficiency.

Highlights

Sugarcane is a commercially important crop in tropical and subtropical regions (Inman-Bamber and Smith, 2005), and is the fifth most important crop in the world (FAOSTAT, 2013)
As ShDJ-overexpression could have affected many genes, we examined the molecular mechanisms modified in transgenic lines under well-watered conditions, considering genes involved in cell wall biosynthesis and water deficit tolerance
We revealed that overexpression of ShDJ gene contributed to drought tolerance, maintaining plant growth and development of transgenic lines under conditions of low water availability

Summary

Introduction

Sugarcane is a commercially important crop in tropical and subtropical regions (Inman-Bamber and Smith, 2005), and is the fifth most important crop in the world (FAOSTAT, 2013). In Brazil, the world leader in sugarcane production, the crop is cultivated over more than 9 million hectares, and the estimated production for the 2018/2019 season is around 365 million tons (CONAB, 2018). Sugarcane production has been affected by unfavorable climatic conditions, which are increasing in frequency and intensity. Drought is an important abiotic stress that negatively impacts sugarcane productivity (Zhao and Li, 2015). This can be, due to water shortage even in rainy seasons or to the expansion of sugarcane cultivation to non-traditional planting regions, such as the Brazilian Cerrado (droughtprone conditions). A challenge for sugarcane breeding programs is to develop cultivars with high productivity under water scarcity

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Discussion

Conclusion