Abstract
BackgroundCalvin cycle plays a crucial role in carbon fixation which provides the precursors of organic macromolecules for plant growth and development. Currently, no gene involved in Calvin cycle has been identified in monocotyledonous plants through mutant or/and map-based cloning approach.ResultsHere, we isolated a low-tillering mutant, c6635, in rice (Oryza sativa). The mutant displayed light green leaves and intensely declined pigment contents and photosynthetic capacity at early growth stage. Moreover, its individual plant showed a much smaller size, and most individuals produced only two tillers. At mature stage, its productive panicles, grain number and seed setting rate were significantly decreased, which lead to a sharp reduction of the grain yield. We confirmed that a single nucleotide mutation in LOC_Os04g16680 gene encoding sedoheptulose 1,7-bisphosphatase (SBPase) involved in Calvin cycle was responsible for the mutant phenotype of c6635 through map-based cloning, MutMap analysis and complementation experiments. Sequence analysis suggested that the point mutation caused an amino acid change from Gly-364 to Asp at the C-terminal of SBPase. In addition, OsSBPase gene was mainly expressed in leaf, and the encoded protein was located in chloroplast. The mutation of OsSBPase could significantly affect expression levels of some key genes involved in Calvin cycle.ConclusionsWe successfully identified a SBPase gene in monocotyledonous plants. Meanwhile, we demonstrated that a single nucleotide substitution at the 3′-end of this gene severely affects plant growth and grain yield, implying that the Gly-364 at the C-terminal of SBPase could play an important role in SBPase function in rice.
Highlights
Calvin cycle plays a crucial role in carbon fixation which provides the precursors of organic macromolecules for plant growth and development
The grain yield of c6635 was sharply reduced by 87.5% (Figs. 1d, 2h)
The results suggested that the mutation in c6635 severely affected plant growth and grain yield
Summary
Calvin cycle plays a crucial role in carbon fixation which provides the precursors of organic macromolecules for plant growth and development. The energy that human and other life on Earth depend on originally come from the Sun. Photosynthesis, as the sole biological process converting solar energy into chemical energy, is of great importance for human survival. Over 90 % of crop biomass is derived from photosynthetic products [1]. Photosynthesis efficiency of crop plants is a key factor for crop yield. Photosynthesis encompasses light reactions and dark reactions which are called carbon fixation reactions. In the five carbon fixation pathways of autotrophs, Calvin cycle is the only biosynthetic process used in plants [2]. Photosynthetic carbon assimilation is inefficient in Calvin cycle of C3 plants, which is a limiting factor for crop yields [3, 4]
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