English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

The research described herein, focuses on investigating the role of pyruvate phosphate dikinase (PPDK) and factors influencing its activity in maize starchy endosperm (SE) tissue. PPDK reversibly converts phosphoenolpyruvate (PEP), pyrophosphate (PPi), and AMP, to pyruvate, phosphate (Pi), and ATP. PPDK is found in microorganisms and plant tissues with diverse functions. PPDK is abundant in maize SE during grain fill, but little is known about its role. Hypotheses were tested using transposon-insertion alleles affecting individual genes and by eliminating all PPDK expression using RNAi. PPDK's C4 metabolism function in mesophyll was proven to be essential in maize. RNAi transgenes completely eliminated PPDK protein and enzyme activity from developing SE. An opaque kernel phenotype resulted, indicative of changes in storage compound organization. Metabolite analyses indicated PPDK acts in the pyruvate-forming direction but is not necessary for synthesis of sufficient ATP to generate normal storage compound abundance. PPDK activity affects energy charge, i.e., ATP/(ADP + AMP) ratio, and through this is proposed to regulate central metabolic fluxes. PPDK activity in SE decreases during prolonged growth in high temperature, coincident with kernel weight decrease compared to normal. Recombinant PPDK was used to test whether this effect is inherent to the enzyme. When incubated without substrates, PPDK maintained full activity up to 35C, but was completely inactivated within 5 min at 45C. Pre-incubation with AMP prevented PPDK from inactivation at 45C. The data suggest PPDK activity in vivo can be affected by availability of AMP, and confirm that PPDK is a particularly temperature-labile enzyme that could contribute to reduced plant

Functions of maize genes encoding pyruvate orthophosphate dikinase in developing maize endosperm and their enzymatic properties