Transcription factor bZIP65 delays flowering via suppressing Ehd1 expression in rice.

Flowering time is one of the most fundamental factors that determine the distribution and final yield of rice. Ehd1 (Early heading date 1) is a B-type response regulator which functions as a flowering time activator. Although diverse flowering time genes have been reported as regulatory factors of Ehd1 expression, the potential regulators of Ehd1 largely remain to be identified. Here, we identified a basic leucine zipper transcription factor bZIP65, a homolog of bZIP71, as a new negative regulator of Ehd1. The overexpression of bZIP65 delays flowering, while bzip65 mutants have similar flowering time to SJ2 (Songjing2) in both long-day and short-day conditions. Biochemically, bZIP65 associates with Ehd1 promoter and transcriptionally represses the expression of Ehd1. Moreover, we found that bZIP65 enhances H3K27me3 level of Ehd1. Taken together, we cloned a new gene, bZIP65, regulating rice heading date, and uncovered the mechanism of bZIP65 delaying flowering time, where bZIP65 increases the H3K27me3 level of Ehd1 and transcriptionally represses the expression of Ehd1, similar to its homolog bZIP71. Supplementary Information: The online version contains supplementary material available at 10.1007/s11032-022-01334-4.

Integration of Metabolomics and Transcriptomics for Investigating the Tolerance of Foxtail Millet (Setaria italica) to Atrazine Stress.

Foxtail millet (Setaria italica) is a monotypic species widely planted in China. However, residual atrazine, a commonly used maize herbicide, in soil, is a major abiotic stress to millet. Here, we investigated atrazine tolerance in millet based on the field experiments, then obtained an atrazine-resistant variety (Gongai2, GA2) and an atrazine-sensitive variety (Longgu31, LG31). To examine the effects of atrazine on genes and metabolites in millet plants, we compared the transcriptomic and metabolomic profiles between GA2 and LG31 seedling leaves. The results showed that 2,208 differentially expressed genes (DEGs; 501 upregulated, 1,707 downregulated) and 192 differentially expressed metabolites (DEMs; 82 upregulated, 110 downregulate) were identified in atrazine-treated GA2, while in atrazine-treated LG31, 1,773 DEGs (761 upregulated, 1,012 downregulated) and 215 DEMs (95 upregulated, 120 downregulated) were identified. The bioinformatics analysis of DEGs and DEMs showed that many biosynthetic metabolism pathways were significantly enriched in GA2 and LG31, such as glutathione metabolism (oxiglutatione, γ-glutamylcysteine; GSTU6, GSTU1, GSTF1), amino acid biosynthesis (L-cysteine, N-acetyl-L-glutamic acid; ArgB, GS, hisC, POX1), and phenylpropanoid biosynthesis [trans-5-o-(4-coumaroyl)shikimate; HST, C3'H]. Meanwhile, the co-expression analysis indicated that GA2 plants had enhanced atrazine tolerance owing to improved glutathione metabolism and proline biosynthesis, and the enrichment of scopoletin may help LG31 plants resist atrazine stress. Herein, we screened an atrazine-resistant millet variety and generated valuable information that may deepen our understanding of the complex molecular mechanism underlying the response to atrazine stress in millet.