Wheat puroindolines tether to starch granule surfaces in puroindoline-null (Pin-null) plants

The interaction of wheat puroindolines (pin) with starch granules from a pin-null cereal crop, rice, was investigated using an in vitro immunofluorescent method. Rice seed cross-sections were incubated with soft (Augusta) and hard (Langdon) durum wheat extracts. The in vitro localization of puroindolines on rice seed cross sections were compared to the in vivo localization of puroindolines from transgenic Pin+ rice seeds using the Durotest anti-Pin monoclonal antibody. Wheat puroindolines were observed to localize with high affinity for rice starch granule surfaces both in vitro and in vivo. The strong interactions of puroindolines with starch granules plays important roles in both plant defense and grain texture. The obtained results confirmed that puroindolines interact with starch granule surfaces in rice, a pin-null cereal, and that an in vitro localization method can be used to predict the in vivo targeting and deposition of puroindoline proteins.