Abstract
Maize kernels are the harvested portion of the plant and are related to the yield and quality of maize. The endosperm of maize is a large storage organ that constitutes 80–90% of the dry weight of mature kernels. Maize kernels have long been the study of cereal grain development to increase yield. In this study, a natural mutation that causes abnormal kernel development, and displays a shrunken kernel phenotype, was identified and named “shrunken 2008 (sh2008)”. The starch grains in sh2008 are loose and have a less proteinaceous matrix surrounding them. The total storage protein and the major storage protein zeins are ~70% of that in the wild-type control (WT); in particular, the 19 kDa and 22 kDa α-zeins. Map-based cloning revealed that sh2008 encodes a GT-2 trihelix transcription factor, ZmThx20. Using CRISPR/Cas9, two other alleles with mutated ZmThx20 were found to have the same abnormal kernel. Shrunken kernels can be rescued by overexpressing normal ZmThx20. Comparative transcriptome analysis of the kernels from sh2008 and WT showed that the GO terms of translation, ribosome, and nutrient reservoir activity were enriched in the down-regulated genes (sh2008/WT). In short, these changes can lead to defects in endosperm development and storage reserve filling in seeds.
Highlights
IntroductionAs a large storage organ in maize, the endosperm contributes to 80–90% of the dry weight in mature maize grains [2,3] and consists of 8–11%
The differences between the wild-type (WT) and mutant kernels could be distinguished from the transmission of the kernel blister stage (approximately 10 to 14 days after pollination (DAP)) to the kernel milk stage (18 to 22 DAP)
To understand the molecular basis of this mutant, we isolated the sh2008 gene by map-based cloning and found that it encoded a member of the trihelix family transcription factor ZmThx20
Summary
As a large storage organ in maize, the endosperm contributes to 80–90% of the dry weight in mature maize grains [2,3] and consists of 8–11%
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