In situ mapping of the effect of additional mutations on starch granule structure in amylose-extender (ae) maize kernels

• Starch granule structure has been probed within GEMS-0067 and wx-ae maize kernels.
• The ae mutation gives rise to heterogeneous starch structure within granules.
• Heterogeneity occurs within, between granules, and between cells in the kernel.
• The HAM gene restricts the volume within the kernel containing heterogeneous granules.
• The wx-ae mutant shows similar heterogeneity to the ae mutant.

Optical (KI/I2-staining, polarised) and FTIR microscopy has been used to monitor starch granule structure within wild-type (wt), GEMS-0067 and waxy-amylose-extender (wx-ae) maize mutant kernels. In the GEMS-0067 mutant containing the high amylose modifier (HAM) gene(s) plus the recessive ae gene, structural heterogeneity characteristic of the ae mutation was reduced markedly. However, enhanced variation in granule shape and size was observed distributed spatially within the kernel, which appears to be related to new heterogeneity in internal starch granule structure. In wx-ae starch mutants the ae gene led to heterogeneity of starch granule structure equivalent to that in single ae mutants, plus new structural heterogeneity coincident with novel induced variation in granule size and shape.