Fragrance of the rice grain achieved via artificial microRNA‐induced down‐regulation of OsBADH2

With 6 figures and 1 table Abstract 2‐acetyl‐1‐pyrroline (2AP) is the principal compound responsible for grain fragrance in rice. In fragrant rice cultivars, BADH2 (betaine‐aldehyde dehydrogenase 2) is inactivated. Here, we describe the effect of amiRNA (artificial microRNA) transgenesis targeted at BADH2 in rice. BADH2 (but not BADH1 ) expression was down‐regulated in transgenic lines where the amiRNA was driven by the maize ubiquitin promoter, and in these lines, grain 2AP content was also significantly elevated; meanwhile, 2AP could not be detected in the grain of wild‐type lines. The leaf proline content in the transgenics was increased through the simultaneous down‐regulation of PRODH and up‐regulation of P5CS . In transgenic lines where the same amiRNA was driven by the endosperm‐specific promoter GluC, no effect on BADH2 expression was detectable, and the content of grain 2AP did not differ from that present in wild‐type grains.