Abstract
BackgroundHigher plants exhibit a remarkable phenotypic plasticity to adapt to adverse environmental changes. The Greater Duckweed Spirodela, as an aquatic plant, presents exceptional tolerance to cold winters through its dormant structure of turions in place of seeds. Abundant starch in turions permits them to sink and escape the freezing surface of waters. Due to their clonal propagation, they are the fastest growing biomass on earth, providing yet an untapped source for industrial applications.ResultsWe used next generation sequencing technology to examine the transcriptome of turion development triggered by exogenous ABA. A total of 208 genes showed more than a 4-fold increase compared with 154 down-regulated genes in developing turions. The analysis of up-regulated differential expressed genes in response to dormancy exposed an enriched interplay among various pathways: signal transduction, seed dehydration, carbohydrate and secondary metabolism, and senescence. On the other side, the genes responsible for rapid growth and biomass accumulation through DNA assembly, protein synthesis and carbon fixation are repressed. Noticeably, three members of late embryogenesis abundant protein family are exclusively expressed during turion formation. High expression level of key genes in starch synthesis are APS1, APL3 and GBSSI, which could artificially be reduced for re-directing carbon flow from photosynthesis to create a higher energy biomass.ConclusionsThe identification and functional annotation of differentially expressed genes open a major step towards understanding the molecular network underlying vegetative frond dormancy. Moreover, genes have been identified that could be engineered in duckweeds for practical applications easing agricultural production of food crops.
Highlights
Higher plants exhibit a remarkable phenotypic plasticity to adapt to adverse environmental changes
We chose fronds and developing turions with 3 days after abscisic acid (ABA) treatment instead of 14 days because 14-day treatment is not a key transition state and RNA purification is greatly hampered by high content of starch, but mature turions with 14-days treatment provide a more complete structural image through transmission electron microscopy (TEM)
Late embryogenesis abundant protein (LEA) genes are a valuable marker for dormancy On the other hand, we found some specific mRNAs were increased in developing turions, for example LEAs
Summary
Higher plants exhibit a remarkable phenotypic plasticity to adapt to adverse environmental changes. Abundant starch in turions permits them to sink and escape the freezing surface of waters. Due to their clonal propagation, they are the fastest growing biomass on earth, providing yet an untapped source for industrial applications. Unlike animals, do not have a fur or can seek shelter to survive under food shortage and cold weather. They adapt to dormancy to avoid adverse environments, such as poor nutrition, chilling temperature, and drought. Dormancy is a complex state of plant development, in which the plant body exhibits little or no growth. Studies on the molecular mechanisms of bud dormancy transitions in perennial woody plants have been conducted, including pear [5], oak [6], and poplar [7]
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