Transcriptomic analysis of transgressive segregants revealed the central role of photosynthetic capacity and efficiency in biomass accumulation in sugarcane

Ratnesh Singh,Ching Man Wai,John Jifon,Chifumi Nagai,Tyler Jones,Qingyi Yu,Ray Ming

doi:10.1038/s41598-018-22798-5

Abstract

Sugarcane is among the most efficient crops in converting solar energy into chemical energy. However, due to its complex genome structure and inheritance, the genetic and molecular basis of biomass yield in sugarcane is still largely unknown. We created an F2 segregating population by crossing S. officinarum and S. spontaneum and evaluated the biomass yield of the F2 individuals. The F2 individuals exhibited clear transgressive segregation in biomass yield. We sequenced transcriptomes of source and sink tissues from 12 selected extreme segregants to explore the molecular basis of high biomass yield for future breeding of high-yielding energy canes. Among the 103,664 assembled unigenes, 10,115 and 728 showed significant differential expression patterns between the two extreme segregating groups in the top visible dewlap leaf and the 9th culm internode, respectively. The most enriched functional categories were photosynthesis and fermentation in the high-biomass and the low-biomass groups, respectively. Our results revealed that high-biomass yield was mainly determined by assimilation of carbon in source tissues. The high-level expression of fermentative genes in the low-biomass group was likely induced by their low-energy status. Group-specific expression alleles which can be applied in the development of new high-yielding energy cane varieties via molecular breeding were identified.

Highlights

Officinarum, S. barberi, and S. sinense have been used for sugar production before modern sugarcane breeding programs via interspecific hybridization started near the end of the 19th century
Saccharum spontaneum is listed as a Federal Noxious Weed by USDA-APHIS and is prohibited from field planting
A strong correlation between the stalk volumes collected at 8.5-month old and the dry weight collected at 1-year old was observed with the correlation coefficient calculated at 0.86

Summary

Introduction

Officinarum, S. barberi, and S. sinense have been used for sugar production before modern sugarcane breeding programs via interspecific hybridization started near the end of the 19th century. The major breakthrough in modern sugarcane breeding was introgression of resistance genes for biotic and abiotic stresses from the wild species S. spontaneum into the domesticated high-sugar species S. officinarum by interspecific hybridizations. Plant biomass yield is a complex trait that is controlled by many external factors (e.g. incident solar radiation, moisture and nutrient supply, etc.) and plant processes such as light interception efficiency, energy conversion efficiency, photosynthetic carbon dioxide assimilation, carbon partitioning efficiency, source-sink balance etc.[19]. Source and sink metabolism are tightly coupled to avoid imbalances between supply and demand[20,21,22]. In many plants, including sugarcane, photosynthetic performance in source leaves is regulated by sink strength[21,22]

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Discussion

Conclusion