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Chinese wild rice (Zizania latifolia) is rich in phenolic compounds, particularly flavonoids. This study identified 203 basic helix‐loop‐helix (bHLHs) in Z. latifolia and showed that ZlbHLH196 (Zla16G011250) corresponds to the ZlRc gene in Z. latifolia, with its protein product localizing to the nucleus. Notably, the pericarps of ZlRc‐overexpressing (OE) rice are brown, whereas those of wild‐type (WT) rice are nonpigmented. The total phenolic, flavonoid, and proanthocyanidin contents, antioxidant activity, as well as enzyme inhibitory effects of ZlRc‐OE rice were significantly higher than those of WT rice. Overall, 221 differential phenolic metabolites were identified between ZlRc‐OE and WT rice, among which 198 were upregulated in the former. Additionally, a total of 227 differentially expressed genes were identified between ZlRc‐OE and WT rice, with 173 upregulated. Kyoto Encyclopedia of Genes and Genomes annotation and enrichment analysis of phenolic metabolites revealed enhanced isoflavonoid, flavone, flavonol, and flavonoid biosynthesis pathways in ZlRc‐OE rice, which, furthermore, showed a markedly upregulated expression and significantly higher activities of four key flavonoid biosynthesis–related enzymes (phenylalanine ammonia‐lyase, chalcone synthase, chalcone‐flavanone isomerase, and dihydroflavonol 4‐reductase). These findings show that ZlRc‐overexpression promotes phenolic compound accumulation in rice seeds and can be used to bioaugment rice phenolic content.

The loss of seed shattering is an important event in crop domestication, and elucidating the genetic mechanisms underlying seed shattering can help reduce yield loss during crop production. This study is the first to systematically identify and analyse the BELL family of transcription factor-encoding genes in Chinese wild rice (Zizania latifolia). ZlqSH1a (Zla04G033720) and ZlqSH1b (Zla02G027130) were identified as key candidate genes involved in seed shattering in Z. latifolia. These genes were involved in regulating the development of the abscission layer (AL) and were located in the nucleus of the cell. Over-expression of ZlqSH1a and ZlqSH1b resulted in a complete AL between the grain and pedicel and significantly enhanced seed shattering after grain maturation in rice. Transcriptome sequencing revealed that 172 genes were differentially expressed between the wild type (WT) and the two transgenic (ZlqSH1a and ZlqSH1b over-expressing) plants. Three of the differentially expressed genes related to seed shattering were validated using qRT-PCR analysis. These results indicate that ZlqSH1a and ZlqSH1b are involved in AL development in rice grains, thereby regulating seed shattering. Our results could facilitate the genetic improvement of seed-shattering behaviour in Z. latifolia and other cereal crops.

Wild rice (Zizania spp.), an aquatic grass belonging to the subfamily Gramineae, has a high economic value. Zizania provides food (such as grains and vegetables), a habitat for wild animals, and paper-making pulps, possesses certain medicinal values, and helps control water eutrophication. Zizania is an ideal resource for expanding and enriching a rice breeding gene bank to naturally preserve valuable characteristics lost during domestication. With the Z. latifolia and Z. palustris genomes completely sequenced, fundamental achievements have been made toward understanding the origin and domestication, as well as the genetic basis of important agronomic traits of this genus, substantially accelerating the domestication of this wild plant. The present review summarizes the research results on the edible history, economic value, domestication, breeding, omics research, and important genes of Z. latifolia and Z. palustris over the past decades. These findings broaden the collective understanding of Zizania domestication and breeding, furthering human domestication, improvement, and long-term sustainability of wild plant cultivation.