Glycolysis stimulation and storage protein accumulation are hallmarks of maize (Zea mays L.) grain filling

Abstract

Maize (Zea mays L.) is a major dietary source of human caloric intake. Grain filling, the developmental stage of the seed during which starch and proteins accumulate, is of great interest in plant biology and agronomy. However, proteomic datasets covering maize seed development, especially during grain filling, are much scarcer than transcriptomic datasets, largely due to the labor-intensive and costly nature of the large-scale analysis required for proteomics. Here, we searched for proteins that showed changes in abundance during four time-points covering the middle stages of grain filling by two-dimensional electrophoresis, MALDI-TOF, and database searches. We detected 1384 protein spots, of which 48 exhibited differential accumulation during grain filling. Of those, we identified the underlying protein for 32 spots: they included enzymes of carbohydrate metabolism, stress-related proteins, and storage proteins, the latter of which represented 34% of all changing proteins during grain filling. Proteins related to carbohydrate metabolism reached their maximum accumulation around 15–20 days after pollination (DAP) and subsequently dropped until 30 DAP. The rise of stress-related proteins such as heat shock proteins demonstrated their involvement in grain filling and seed maturation. This study catalogues the proteome changes during grain filling and provides basic but critical information regarding the biological changes during maize kernel development.

Clostridium acetobutylicum atpG-Knockdown Mutants Increase Extracellular pH in Batch Cultures

“…To see the effects of atpG knockdown on physiological characteristics, we first analyzed and compared cell growth between ATCC 824 and 824-2866KD ( Figure 3 ; Supplementary Figure S3 ). There was no apparent difference in growth between ATCC 824 and 824-2866KD ( Figure 3 ), even though disruption of ATPase is known to reduce ATPase activity and ATP level, which in turn inhibits cell growth in non-clostridia strains ( Iwamoto et al, 1990 ; Ferrandiz and De La Campa, 2002 ; Causey et al, 2003 ; Cipriano et al, 2006 ; Kim et al, 2020 ).…”

“…After such phase transition, the function of hydrogenase is turned-off, and NAD + is regenerated by 4 and 2 dehydrogenases for butanol and ethanol biosynthesis, respectively ( Tremblay et al, 2012 ; Fast and Papoutsakis, 2018 ) (see Figure 1 for details). Continuous acid re-assimilation and carbon flux toward solvent production cause the lowered external pH to rise ( Kim et al, 2020 ; Li et al, 2020 ).…”

The molecular basis of cereal grain proteostasis

“…Significant interest has been paid to understanding the role of protein synthesis and degradation during protein accumulation in cereal grains. The majority of this work is based on measuring changing patterns of protein abundance in time course proteomics experiments, and matching this to related changes in transcriptomics and metabolomics experiments [37][38][39][40][41][42][43]. Proteins that are required for cell division, cell wall formation, and cell growth, such as cytoskeleton proteins, histones, and xyloglucan endotransglucosylases/hydrolases accumulate in the early stage of grain development [42,44,45].…”

“…During the grain filling stage, the accumulation of these cell growth/division related proteins stops and the degradation of them begins. The accumulation of grain storage proteins, enzymes for starch synthesis, protein synthesis machinery, and factors for protein folding and post-translational modification of storage proteins increases dramatically during the short period that begins from grain filling [ 14 , 39 , 45 ]. Once grain starch and storage proteins reached their maximum abundance, the grain maturation stage begins during which ubiquitin is accumulated and activated to facilitate the recycling of unwanted proteins.…”

“…In maize, over 90% of the storage proteins accumulate during the grain filling stage from 8 to 34 DPA. Zeins, the most abundant storage proteins in maize, rapidly and steadily accumulate in abundance across the entire grain filling stage, and the abundance of globulins and vicilin-like proteins increase more than 10-fold from 15 and 30 DPA [ 39 , 54 ]. During the same time period, the abundance of carbohydrate metabolism-related proteins increase from 15 to 25 DPA, followed by a decrease from 30 DPA onwards [ 39 ].…”