Expression of a Codon-Optimized dsdA Gene in Tobacco Plastids and Rice Nucleus Confers D-Serine Tolerance.

Yanmei Li,Shizhan Lu,Yongjun Lin,Juanjuan Zhang,Rui Wang,Zongliang Hu,Fei Zhou,Hongcai Li

doi:10.3389/fpls.2016.00640

Yanmei Li, Shizhan Lu + Show 6 more

Open Access

https://doi.org/10.3389/fpls.2016.00640

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Abstract

D-serine is toxic to plants. D-serine ammonia lyase, which is encoded by the dsdA gene, can attenuate this toxicity with high specificity. In the present study, we explored the function of codon-optimized dsdA with tobacco plastids and rice nuclear transformation system. It was shown that dsdA gene was site-specifically integrated into the tobacco plastid genome and displayed a high level of expression. Genetic analysis of the progenies showed that dsdA gene is maternally inherited and confers sufficient D-serine resistance in tobacco. The effective screening concentrations of D-serine for seed germination, callus regeneration and foliar spray were 10, 30, and 75 mM, respectively. In addition, calluses from homozygous transgenic rice lines also showed significant tolerance to D-serine (up to 75 mM). Our study proves the feasibility of using dsdA gene as a selectable marker in both plastid and nuclear transformation systems.

Highlights

As the essential organelle for photosynthesis, chloroplast has attracted great research interests
To explore the potential of D-serine to be used for selecting and screening transplastomic plants, we investigated the function of D-serine tolerance gene dsdA, which encodes D-serine ammonia lyase in transplastomic lines
As many crops are endogenously resistant to streptomycin and spectinomycin (Khan and Maliga, 1999; Li, 2013), spectinomycin cannot be used for selection in the plastid transformation of such crops

Summary

Introduction

As the essential organelle for photosynthesis, chloroplast has attracted great research interests. Plastid genome is characterized by high copy number, which provides a platform for the high-level expression of exogenous genes (Lee et al, 2003; Koya et al, 2005; Oey et al, 2009a; Li et al, 2013). Their maternal inheritance property greatly reduces cross-pollination and decreases the risk of biosecurity (Ruf et al, 2007; Schneider et al, 2015). Over the past several decades, plastid transformation has been successfully applied in dicotyledonous plants (Ruf et al, 2001; Craig et al, 2008; Scotti et al, 2009; Soria-Guerra et al, 2009), including the application of bioreactors (Kolotilin et al, 2012; Clarke et al, 2013; Gorantala et al, 2014; Hassan et al, 2014) and the improvement of agronomic traits in different plant species, such as resistance to herbicides (Ye et al, 2001; Kang et al, 2003) and insects (Hou et al, 2003; Liu et al, 2008; Zhang et al, 2015a), tolerance to salt (Kumar et al, 2004), and drought (Lee et al, 2003)

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