Engineering chloroplast development in rice through cell‐specific control of endogenous genetic circuits


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Authors
Lee, Dong‐Yeon 
Hua, Lei 
Khoshravesh, Roxana 
Giuliani, Rita 
Kumar, Indrajit 
Abstract

Summary: The engineering of C4 photosynthetic activity into the C3 plant rice has the potential to nearly double rice yields. To engineer a two‐cell photosynthetic system in rice, the rice bundle sheath (BS) must be rewired to enhance photosynthetic capacity. Here, we show that BS chloroplast biogenesis is enhanced when the transcriptional activator, Oryza sativa Cytokinin GATA transcription factor 1 (OsCGA1), is driven by a vascular specific promoter. Ectopic expression of OsCGA1 resulted in increased BS chloroplast planar area and increased expression of photosynthesis‐associated nuclear genes (PhANG), required for the biogenesis of photosynthetically active chloroplasts in BS cells of rice. A further refinement using a DNAse dead Cas9 (dCas9) activation module driven by the same cell‐type specific promoter, directed enhanced chloroplast development of the BS cells when gRNA sequences were delivered by the dCas9 module to the promoter of the endogenous OsCGA1 gene. Single gRNA expression was sufficient to mediate the transactivation of both the endogenous gene and a transgenic GUS reporter fused with OsCGA1 promoter. Our results illustrate the potential for tissue‐specific dCas9‐activation and the co‐regulation of genes needed for multistep engineering of C4 rice.

Description
Keywords
Original Article, Original Articles, C4 photosynthesis, dCas9‐mediated transcriptional activation, rice bundle sheath, chloroplast development
Journal Title
Plant Biotechnology Journal
Conference Name
Journal ISSN
1467-7644
1467-7652
Volume Title
Publisher
Sponsorship
Bill and Melinda Gates Foundation (Grant ID#51586, OPP1129902)
NSF (MCB‐1546882)