Downregulation of the CpSRP43 gene expression confers a truncated light-harvesting antenna (TLA) and enhances biomass and leaf-to-stem ratio in Nicotiana tabacum canopies
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Downregulation in the expression of the signal recognition particle 43 (SRP43) gene in tobacco conferred a truncated photosynthetic light-harvesting antenna (TLA property), and resulted in plants with a greater leaf-to-stem ratio, improved photosynthetic productivity and canopy biomass accumulation under high-density cultivation conditions.
Evolution of sizable arrays of light-harvesting antennae in all photosynthetic systems confers a survival advantage for the organism in the wild, where sunlight is often the growth-limiting factor. In crop monocultures, however, this property is strongly counterproductive, when growth takes place under direct and excess sunlight. The large arrays of light-harvesting antennae in crop plants cause the surface of the canopies to over-absorb solar irradiance, far in excess of what is needed to saturate photosynthesis and forcing them to engage in wasteful dissipation of the excess energy. Evidence in this work showed that downregulation by RNA-interference approaches of the Nicotiana tabacum signal recognition particle 43 (SRP43), a nuclear gene encoding a chloroplast-localized component of the photosynthetic light-harvesting assembly pathway, caused a decrease in the light-harvesting antenna size of the photosystems, a corresponding increase in the photosynthetic productivity of chlorophyll in the leaves, and improved tobacco plant canopy biomass accumulation under high-density cultivation conditions. Importantly, the resulting TLA transgenic plants had a substantially greater leaf-to-stem biomass ratio, compared to those of the wild type, grown under identical agronomic conditions. The results are discussed in terms of the potential benefit that could accrue to agriculture upon application of the TLA-technology to crop plants, entailing higher density planting with plants having a greater biomass and leaf-to-stem ratio, translating into greater crop yields per plant with canopies in a novel agronomic configuration.
KeywordsCanopy density Chlorophyll-deficient mutant Light-harvesting antenna size Productivity TLA technology
Truncated light-harvesting antenna
Nicotiana tabacum TLA3-CpSRP43 gene downregulation of expression by RNA interference
We thank Hannah Clifton and Christina Wistrom for the greenhouse support they provided during the canopy density experiments. We also thank Dr. Peggy G. Lemaux for access to an ESL-1 cabinet and Dr. Krishna K. Niyogi for use of the LD2/3 electrode for oxygen evolution measurements.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
Human participants and/or animals
Research did not involve human and/or animal subjects. Experimental protocols in this work were approved by the UC Berkeley Committee for Laboratory and Environmental BioSafety (CLEB).
All authors have read and approved submission of this work.
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