Rice seed storage protein is a key nutrient component, providing essential amino acids crucial for human nutrition and a nitrogen source for developing plant seedlings. Prolamin, accounting for 20-30% of the total seed storage proteins, accumulates in...
Rice seed storage protein is a key nutrient component, providing essential amino acids crucial for human nutrition and a nitrogen source for developing plant seedlings. Prolamin, accounting for 20-30% of the total seed storage proteins, accumulates in ER-derived protein bodies (PB-I). Prolamins are categorized into three groups by molecular size (10, 13, or 16 kDa), while the 13 kDa prolamins are assigned to four subgroups (Pro13a-I, Pro13a-II, Pro13b-I, and Pro13b-II) based on cysteine residue content. Here, we generated four knockout strains of rice using CRISPR-Cas9, named 1a-8-1, 2a-2-1, 4b-9-7, and 8b-3-9, each of which demonstrated selectively reduced expression of specific subgroups of the 13 kDa prolamins (Pro13a-I, Pro13a- I, Pro13b-I/II, and Pro13b-I, respectively). These four mutant rice lines also showed the compensatory expression of glutelins and non-targeted prolamins and were accompanied by low grain weight, altered starch content, and atypically-shaped starch granules and protein bodies. Transcriptome analysis identified 927 transcripts that were differentially expressed in the mutant rice lines during development. Subsequently, a Pearson correlation analysis was conducted among 927 DEGs and 13 kDa prolamin genes, revealing 746 transcripts with a correlation coefficient of ≥|0.7|. A correlation network was established, involving transcripts mainly associated with RNA processing, RNA transcription, protein synthesis, protein folding, protein degradation, protein targeting, protein posttranslational modification, stress response, and transport functions. Analysis of this network revealed a negative correlation between genes in the Pro13a-I subgroup and those in the Pro13a-II and Pro13b-I/II subgroups. Moreover, the alterations in the transcription levels of 9 ER stress and 17 transcription factor genes was also observed in mutant rice in which expression of 13 kDa prolamin genes was suppressed. Our results provide valuable insight into the regulatory mechanisms underlying rice seed development and the specific roles played by 13 kDa rice prolamins and their target genes.