Molecular structural differences between maize leaf and endosperm starches

Abstract

Highlights Leaf starch has much shorter amylopectin chains than endosperm starch  Leaf starch has much smaller molecules than endosperm starch  Leaf starch granules are smaller than endosperm granules  Differences between leaf and endosperm starch related to their biosynthesis process 3 AbstractThe morphology, whole molecular size distribution and chain-length distribution of maize leaf starch have been characterized and compared to its endosperm starch, to better understand differences between leaf and endosperm starch structure, and the relationship with the functions of starch in these organs. Leaf starch is found to have amylopectin with much shorter chains (virtually none with a degree of polymerization, DP, above 70) than the endosperm amylopectin, which has significant numbers of chains with DP up to ~120, and has much smaller molecular size (and is present at a much lower amount) than endosperm starch. It is postulated that these pronounced differences arise from the distinct starch synthesis pathways in these organs, and are consistent with the starches" distinct botanical functions: short-term storage requiring relatively rapid degradation for leaf starch, and high crystallinity and high energy density requiring slow degradation for endosperm starch.

A rapid and universal method for isolating starch granules in plant tissues

“…Starch with a high amylopectin content could form gels with a low trend to retrogradation (Yuan, Thompson, & Boyer, ). Thus, the great difference in amylose content among the three kinds of maize SGs (Figure b) would affect the physiochemical, structural, and functional properties (e.g., gelatinization temperature) of these SGs (Liu et al, ); this is consistent with previous observations that larger SGs contain more amylose than smaller ones in maize endosperm (Cai et al, ; Utrilla‐Coello, Agama‐Acevedo, de la Rosa, Rodriguez‐Ambriz, & Bello‐Perez, ) and that much shorter chains of amylopectin are present in maize leaf SGs than in endosperm SGs (Yu et al, ). The gelatinization temperature of maize pollen SGs was significantly higher than that in SGs of maize endosperm and leaves, which could not be explained only by amylose content difference.…”

“…In Arabidopsis, chloroplasts in mature leaves typically contain five to seven SGs (Crumpton‐Taylor, Grandison, Png, Bushby, & Smith, ). Unlike storage SGs, leaf SGs are small (typically 2 μm), and those examined so far exhibit a uniformly flattened disc shape (Seung et al, ; Yu, Zhang, Li, & Gilbert, ; Zeeman et al, ). Isolation of high‐quality SGs from different plant tissues is an essential prerequisite for studying the properties, structure, and components of SGs; identifying SG‐associated proteins that are involved in starch metabolism; and further exploring the roles of SGs in abiotic stress.…”

“…However, the methods employed to isolate Arabidopsis leaf SGs do not work well for the leaves of crop plants, which contain large amounts of cellulose and semicellulose. Only one study on the isolation of SGs from crop leaves (maize; Yu et al, ) has been reported to date, but the quality of the purified leaf SGs was poor, as indicated by SEM of a single granule.…”

Starch and Glycogen Analyses: Methods and Techniques

“…The size of the starch granules isolated from different species also varies widely from below 1 µm up to several 100 µm [45,46]. For example, transitory starch granules are mostly in a range below 7 µm having a flat, discoid, or slightly round shape [47][48][49][50][51]. Starch granules from different storage organs have a bigger variability in size and shape, e.g., potato (Solanum tuberosum L.) starch granules are spherical with up to 100 µm in diameter.…”

Comparison of starch granule sizes of maize seeds between parental lines and derived hybrids suggests a maternal inheritance trend

“…Storage starch granule (SG) mainly exists in cereal seeds, storage roots, and tubers, with a highly varied size of 2 to 50 m dependent on plant species (Seung and Smith, 2019). Transient SG is accumulated in leaf chloroplast and is usually small (~2 m) with a uniformly flattened disc shape among plant species (Seung et al, 2017;Yu et al, 2017;Zeeman et al, 2002). The SG with different sizes can be used for specific applications.…”