Deficiency of copper (Cu) causes low fertility in many plant species, but the molecular mechanisms underlying distribution of Cu to the floral organs are poorly understood. Here, we found that a member of yellow-stripe like (YSL) family, YSL16 encoding the Cu-nicotianamine (Cu- NA) transporter, was highly expressed in the rachilla, with less expression in the palea and lemma of rice (Oryza sativa). GUS staining of transgenic rice carrying OsYSL16 promoter-GUS showed that OsYSL16 was mainly expressed in vascular bundles of rachilla as well as palea and lemma. Knockout of OsYSL16 resulted in decreased Cu distribution to the stamens, but increased distribution to the palea and lemma. A short-term (24 h) ⁶⁵Cu-labelling experiment confirmed increased Cu concentration of palea and lemma in the mutant. Furthermore, we found that redistribution of Cu from palea and lemma was impaired in osysl16 mutant after exposure to Cu-free solution. osysl16 mutant showed low pollen germination, but this was rescued by addition of Cu in the medium. Our results indicate that OsYSL16 expressed in the vascular bundles of rachilla is important for preferential distribution of Cu to the stamens, while OsYSL16 in vascular bundles of palea and lemma is involved in Cu redistribution under Cu-limited conditions in rice.

The uptake and transport of iron (Fe) in plants are both important for plant growth and human health. However, little is known about the mechanism of Fe transport in plants, especially for crops. In the present study, the function of yellow stripe-like 13 (YSL13) in rice was analyzed. OsYSL13 was highly expressed in leaves, especially in leaf blades, whereas its expression was induced by Fe deficiency both in roots and shoots. Furthermore, the expression level of OsYSL13 was higher in older leaves than that in younger leaves. OsYSL13 was located in the plasma membrane. Metal measurement revealed that Fe concentrations were lower in the youngest leaf and higher in the older leaves of the osysl13 mutant under both Fe sufficiency and deficiency conditions, compared with the wild type and two complementation lines. Moreover, the Fe concentrations in the brown rice and seeds of the osysl13 mutant were also reduced. Opposite results were found in OsYSL13 overexpression lines. These results suggest that OsYSL13 is involved in Fe distribution in rice.