title: Pyrophosphate-dependent fructose-6-phosphate 1-phosphotransferase induction and attenuation of Hsp gene expression during endosperm modification in quality protein maize.
abstract: Quality Protein Maize (QPM) is a hard-endosperm version of the high-lysine opaque2 (o2) maize (Zea mays) mutant, but the genes involved in modification of the soft o2 endosperm are largely unknown. Pyrophosphate-dependent fructose-6-phosphate 1-phosphotransferase (PFP) catalyzes the ATP-independent conversion of fructose-6-phosphate to fructose-1,6-bisphosphate in glycolysis. We found a large increase in transcript and protein levels of the α-regulatory subunit of PFP (PFPα) in QPM endosperm. In vitro enzyme assays showed a significant increase in forward PFP activity in developing endosperm extracts of QPM relative to the wild type and o2. An expressed retrogene version of PFPα of unknown function that was not up-regulated in QPM was also identified. The elevated expression levels of a number of ATP-requiring heat shock proteins (Hsps) in o2 endosperm are ameliorated in QPM. PFPα is also coinduced with Hsps in maize roots in response to heat, cold, and the unfolded protein response stresses. We propose that reduced ATP availability resulting from the generalized Hsp response in addition to the reduction of pyruvate, orthophosphate dikinase activity in o2 endosperm is compensated in part by increased PFP activity in QPM.
authors.affiliation: Department of Agronomy and Horticulture, University of Nebraska, Lincoln, Nebraska 68588, USA.
authors.forename: Xiaomei
authors.initials: X
authors.lastname: Guo
authors.forename: Kyla
authors.initials: K
authors.lastname: Ronhovde
authors.forename: Lingling
authors.initials: L
authors.lastname: Yuan
authors.forename: Bo
authors.initials: B
authors.lastname: Yao
authors.forename: Madhavan P
authors.initials: MP
authors.lastname: Soundararajan
authors.forename: Thomas
authors.initials: T
authors.lastname: Elthon
authors.forename: Chi
authors.initials: C
authors.lastname: Zhang
authors.forename: David R
authors.initials: DR
authors.lastname: Holding
mesh_terms: D000595:Amino Acid Sequence; D020134:Catalytic Domain; D018076:DNA, Complementary; D056625:Endosperm / Q000378:metabolism*; D004790:Enzyme Induction; D018506:Gene Expression Regulation, Plant; D006360:Heat-Shock Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D010770:Phosphotransferases / Q000096:biosynthesis* / Q000737:chemistry; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D040641:Quantitative Trait Loci; D017386:Sequence Homology, Amino Acid; D003313:Zea mays / Q000235:genetics / Q000378:metabolism*
chemical_list: D018076:DNA, Complementary; D006360:Heat-Shock Proteins; D010940:Plant Proteins; D010770:Phosphotransferases; C022502:pyrophosphate-fructose 6-phosphate 1-phosphotransferase