Puroindolines are associated with decreased polar lipid breakdown during wheat seed development

The wheat Hardness (Ha) locus consists of Puroindoline a (Pina) and Puroindoline b (Pinb) and controls whether wheat is soft or hard textured. PINA and PINB act cooperatively to create grain softness and are associated with increased polar lipids at seed maturity. Here we examined developing seeds varying in PINA or PINB content to identify when polar lipid differences occur. One population carried Wild Type (WT) PINA while varying for the presence of PINB, while the other population carried a WT PINB and segregated for PINA. For the PINB segregating population, polar lipids were maximal on a per mg dry weight basis at 7–14 days after anthesis (DAA) while for PINA segregating population, total polar lipids were maximal at 7–21 DAA. The most abundant polar lipids at maturity were mono- and di- galactosyldiglyceride. No individual polar lipid species were specific to PINA or PINB. The effect of both PINA and PINB increased throughout seed development with greater decreases in the most abundant polar lipids in genotypes lacking either PINA or PINB. The results indicate that PINA and PINB act cooperatively to prevent polar lipid breakdown during seed maturation and that this process is central to the development of grain softness.