Constitutive expression of a wheat microRNA, TaemiR167a, confers male sterility in transgenic Arabidopsis

The miR167 family has been shown to play roles in regulating plant fertility by control the expression of a set of ARF transcription factors. In this study, the precursor of miR167a was cloned from the photo-thermo-sensitive genic male sterile (PTGMS) wheat line BS366. Moreover, we identified the target gene, TaARF8, from PTGMS wheat line BS366, and used the 5-RACE assay to confirm the cleavage site. Overexpression (OE) of TaemiR167a in Arabidopsis induced male sterility phenotypes, and reduced the expression levels of AtARF6 and AtARF8. Meanwhile, OE of TaemiR167a reduced the content of endogenous jasmonic acid (JA) and indole acetic acid (IAA) in transgenic Arabidopsis lines. In PTGMS wheat line BS366, the expression levels of TaemiR167a were up-regulated in anther tissues during pollen development process, while the transcriptional levels of TaARF8 were down-regulated under sterile conditions. Importantly, TaemiR167a was sensitive to low temperature (10 degrees), and was highly expressed in anther tissues of BS366 at pollen developmental stage 3 in sterile environment. Then, we measured the endogenous JA and IAA in BS366 anther tissues, and found that the accumulation of JA and IAA in anther was abnormal during the pollen development process. These results suggested that TaemiR167a-mediated regulation of TaARF8 and changes of endogenous JA and IAA during pollen developmental process took part in the pollen fertility control in PTGMS wheat line BS366.