Analysis of ADP-glucose pyrophosphorylase expression during turion formation induced by abscisic acid in Spirodela polyrhiza (greater duckweed)

BMC Plant Biology

Research Article

Joachim Messing¹  Wenqin Wang² 

[1] Waksman Institute of Microbiology, Rutgers University, 190 Frelinghuysen Road, 08854, Piscataway, NJ, USA;Waksman Institute of Microbiology, Rutgers University, 190 Frelinghuysen Road, 08854, Piscataway, NJ, USA;Department of Plant Biology and Pathology, Rutgers University, 59 Dudley Road, 08901, New Brunswick, NJ, USA;

关键词: Duckweed;    Spirodela;    Starch;    Turion;    ADP-glucose pyrophosphorylase;   

DOI  :  10.1186/1471-2229-12-5

 received in 2011-10-03, accepted in 2012-01-11,  发布年份 2012

来源: Springer

【 摘 要 】

BackgroundAquatic plants differ in their development from terrestrial plants in their morphology and physiology, but little is known about the molecular basis of the major phases of their life cycle. Interestingly, in place of seeds of terrestrial plants their dormant phase is represented by turions, which circumvents sexual reproduction. However, like seeds turions provide energy storage for starting the next growing season.ResultsTo begin a characterization of the transition from the growth to the dormant phase we used abscisic acid (ABA), a plant hormone, to induce controlled turion formation in Spirodela polyrhiza and investigated their differentiation from fronds, representing their growth phase, into turions with respect to morphological, ultra-structural characteristics, and starch content. Turions were rich in anthocyanin pigmentation and had a density that submerged them to the bottom of liquid medium. Transmission electron microscopy (TEM) of turions showed in comparison to fronds shrunken vacuoles, smaller intercellular space, and abundant starch granules surrounded by thylakoid membranes. Turions accumulated more than 60% starch in dry mass after two weeks of ABA treatment. To further understand the mechanism of the developmental switch from fronds to turions, we cloned and sequenced the genes of three large-subunit ADP-glucose pyrophosphorylases (APLs). All three putative protein and exon sequences were conserved, but the corresponding genomic sequences were extremely variable mainly due to the invasion of miniature inverted-repeat transposable elements (MITEs) into introns. A molecular three-dimensional model of the SpAPLs was consistent with their regulatory mechanism in the interaction with the substrate (ATP) and allosteric activator (3-PGA) to permit conformational changes of its structure. Gene expression analysis revealed that each gene was associated with distinct temporal expression during turion formation. APL2 and APL3 were highly expressed in earlier stages of turion development, while APL1 expression was reduced throughout turion development.ConclusionsThese results suggest that the differential expression of APLs could be used to enhance energy flow from photosynthesis to storage of carbon in aquatic plants, making duckweeds a useful alternative biofuel feedstock.

【 授权许可】

CC BY   
© Wang and Messing; licensee BioMed Central Ltd. 2011