Composition of sexual fluids in Cycas revoluta ovules during pollination and fertilization

The composition of fuids that mediate fertilization in cycads is described for the frst time. Using tandem mass spectrometry, proteomes of two stages of fuid pro‑ duction, megagametophyte fuid and archegonial chamber fuid production, are compared in Cycas revoluta. These were compared with the proteome of another sexual fuid produced by ovules, the pollination drop proteins. Cycad ovules pro‑ duce complex liquids immediately prior fertilization. Compared with the pollination drops that mainly had few proteins in classes involved in defense and carbohydrate modifcation, megagametophyte fuid and archegonial chamber fuid had larger pro‑ teomes with many more protein classes, e.g. proteins involved in programmed cell death. Using high-performance liquid chromatography, megagametophyte fuid and archegonial chamber fuid were shown to have elevated concentrations of smaller molecular weight molecules including glucose, pectin and glutamic acid. Compared to megagametophyte fuid, archegonial chamber fuid had elevated pH as well as higher osmolality.