MiR408 Regulates Grain Yield and Photosynthesis via a Phytocyanin Protein

Abstract

Increasing grain yield is the most important object of crop breeding. Here, we report that the elevated expression of a conserved microRNA, OsmiR408, could positively regulate grain yield in rice () by increasing panicle branches and grain number. We further showed that OsmiR408 regulates grain yield by down-regulating its downstream target, , which is an uclacyanin (UCL) gene of the phytocyanin family. The knock down or knock out of also increases grain yield, while the overexpression of results in an opposite phenotype. Spatial and temporal expression analyses showed that was highly expressed in pistils, young panicles, developing seeds, and inflorescence meristem and was nearly complementary to that of OsmiR408. Interestingly, the OsUCL8 protein was localized to the cytoplasm, distinct from a majority of phytocyanins, which localize to the plasma membrane. Further studies revealed that the cleavage of by miR408 affects copper homeostasis in the plant cell, which, in turn, affects the abundance of plastocyanin proteins and photosynthesis in rice. To our knowledge, this is the first report of the effects of miR408- in regulating rice photosynthesis and grain yield. Our study further broadens the perspective of microRNAs and UCLs and provides important information for breeding high-yielding crops through genetic engineering.

A putative AGO protein, OsAGO17, positively regulates grain size and grain weight through OsmiR397b in rice

“…The expression levels of some miRNAs were changed in the OsAGO17 transgenic plants, such as OsmiR156j, OsmiR396c, OsmiR398b and OsmiR408, all of which have been reported to regulate seed development in rice (Jiao et al ., ; Zhang et al ., ,b), so there may be a complex regulatory network associated with OsAGO17. In addition, OsmiR397, OsmiR398 and OsmiR408 also play an important role in abiotic and biotic stress responses (Jia et al ., ; Lu et al ., ; Pan et al ., ).…”

“…MiRNAs have been identified as important regulators of grain size and yield in rice; among these miRNAs, miR397, miR398 and miR408 positively regulate grain size (Zhang et al ., , ,b). AGO is an essential protein that is involved in gene expression regulation through miRNAs (Bartel, ), and it is highly likely that at least one AGO protein is involved in grain size regulation in rice.…”

“…OsmiR398 promotes rice yield by increasing the grain number per panicle, grain size and grain weight (Zhang et al ., ,). OsmiR408 increases panicle branching and grain number to promote rice yield and targets the uclacyanin gene OsUCL18 (Zhang et al ., ,). AGOs are essential for miRNA‐mediated regulation of target gene expression, but it remains unclear which AGO affects these yield‐related characteristics via accumulation of sRNA.…”

“…Meanwhile, OsLAC can affect the sensitivity of BR (Zhang et al ., ). OsmiR398 promotes rice yield by increasing the grain number per panicle, grain size and grain weight (Zhang et al ., ,). OsmiR408 increases panicle branching and grain number to promote rice yield and targets the uclacyanin gene OsUCL18 (Zhang et al ., ,).…”

Overexpression of microRNA408 enhances photosynthesis, growth, and seed yield in diverse plants

“…Recently, a series of genetic manipulations of miR408 in rice have been reported (Zhang et al ; Zhou et al ). It was observed that overexpression of miR408 in rice could positively regulate grain yield via a phytocyanin protein (Zhang et al ). Our reported effects of miR408 in rice are consistent with this previous work.…”