The Structure, Function, and Regulation of Starch Synthesis Enzymes SSIII with Emphasis on Maize

Abstract

Starch biosynthesis is a complex and highly controlled process that requires coordinated activities among multiple enzymes. Starch synthase III (SSIII) is the largest protein in the starch synthase complex and its function is to lengthen long-chain amylopectin in starch synthesis. It potentially affects the activity of other key enzymes in starch synthesis through protein–protein interactions; therefore, its function and regulation play a predominant role in starch synthesis. In this review, we summarized the main research of SSIII including its biochemical characteristics, structural features, expression atlas, and regulation means. Structural features and expressional analysis indicated that SSIIIa is the main functional protein in maize endosperm rather than SSIIIb-a and SSIIIb-b, even though they are similar in the tertiary structures. The regulation investigation of SSIIIa showed that there are 13 transcription factors that control the transcription of SSIIIa. Interaction network analysis showed that SSIIIa could be involved with ten other key enzymes in starch synthesis. In conclusion, this review considerably extends our understanding of SSIII and provides the theoretical basis for improving starch synthesis by SSIII in maize.

Site-Directed Mutations at Phosphorylation Sites in Zea mays PHO1 Reveal Modulation of Enzymatic Activity by Phosphorylation at S566 in the L80 Region

“…Intriguingly, this pattern aligns with key temporal shifts during seed development, with PHO1 expression being initially subdued, escalating to a peak at 12 DAP, and subsequently waning as seed development reaches completion. Notably, the expression dynamics of PHO1 transcripts displayed a similar trajectory to that of various enzymes integral to starch biosynthesis, including SSs, SBEs, and DBEs [ 2 , 31 ]. This further emphasizes the possible role of PHO1 in the regulation of the starch biosynthesis pathway in Zea mays .…”

Effects of Post-Anthesis Irrigation on the Activity of Starch Synthesis-Related Enzymes and Wheat Grain Quality under Different Nitrogen Conditions

“…However, excessive nitrogen application has an adverse effect, causing the wheat to remain green for an extended period and delaying its ripening, which is primarily characterized by a significant reduction in the rate and overall quantity of starch accumulation in wheat grains. This delay is also associated with a decline in the activity of the four enzymes, ultimately resulting in decreased grain weight and yield [ 17 , 18 ].…”