Starch is the highest content component in the grains of wheat and cereal crops, which has an important impact on crop yield, nutritional quality, health value, and processing and utilization. Starch synthase IIa (starch synthase IIa, SSIIa) is a key enzyme in crop starch synthesis. Its absence or deficiency will cause changes in the distribution of amylopectin chain length in wheat and cereal crops, increase in amylose and dietary fiber content, and total starch content And production declines. Studies on important natural variants of SSIIa in rice, corn and other crops have been reported, but there is no research on SSIIa variants of barley with different functions.
Highland barley (naked barley) is the most important national food ration in the Qinghai-Tibet Plateau of my country. It plays an irreplaceable role in the health of Tibetan residents, regional economic development, social stability, and the formation of distinctive culture. The discovery of starch synthase IIa variants in highland barley and the study of its functions are of great significance to the quality improvement, processing and utilization of highland barley and barley, as well as industrial value-added efficiency.
Crop Molecular Breeding Project Team of Chengdu Institute of Biology separated highland barley starch granule binding proteins by electrophoresis, and found two natural variants of SSIIa, combined with mass spectrometry analysis and western blotting to confirm their”identities”, namely SSIIaL and SSIIaH; by coding Gene sequence difference analysis revealed that specific variants were generated due to the 33bp insertion/deletion. Based on this sequence difference, a specific molecular marker that can quickly and accurately identify the two genotypes was developed. Through the reorganization of inbred line population and natural population, the effects of SSIIaL and SSIIaH on starch quality, other grain components and grain characteristics of barley grains were studied, and they were found to be closely related to grain hardness. Studying the distribution of SSIIaL and SSIIaH in wild barley, Australian cultivated barley, barley farm varieties, and barley bred varieties, it is found that the two variants are more consistent in wild barley (14 SSIIaL/16 SSIIaH), and SSIIaH is the absolute majority in Australian cultivated barley Advantages (5 SSIIaL /19 SSIIaH), the proportion of SSIIaL in highland barley is very high, and the bred highland barley varieties and farm varieties SSIIaL/SSIIaH are 46/28 and 41/57 respectively. The differences in the distribution of SSIIaL and SSIIaH in different populations are consistent with barley terminal utilization and breeding selection. Australian cultivated barley is mainly used for beer brewing and feed, with low grain hardness and low energy consumption. SSIIaH genotype is a more favorable choice; Breeding technology in the area is relatively lagging, and eating is the primary goal. Because the high grain hardness index is related to the color of the grain, good nutrition quality and strong resistance, the material with high grain hardness has become the preference of breeders (SSIIaL genotype). This study provides molecular technology and theoretical basis for the selection of highland barley and barley quality-oriented breeding.
The results of the study entitled”Effects of Two Starch Synthase IIa Isoforms on Grain Components and Other Grain Traits in Barley” were published in the Journal of Agricultural and Food Chemistry (DOI:10.1021) on January 23, 2021. /acs.jafc.0c05445) on. Associate researcher Pan Zhifen is the first author and corresponding author of the paper. The research was funded by the second comprehensive scientific investigation and study on the Qinghai-Tibet Plateau (2019QZKK0303) and the provincial and ministerial joint construction of a highland barley and yak key laboratory project (XZNKY-2020-C-007).