Differential Changes in Levels of mRNAs during Maturation of Wheat Seeds That Are Susceptible and Resistant to Preharvest-Sprouting

Seed dormancy is strongly related to the physiological conditions,especially as they relate to responsiveness to ABA, of embryocells during maturation of seeds. In this study, seeds of Triticumaestivum L. cv. Chihoku, which showed nondormancy at harvest,and line Kitakei-l354 (referred to as Kitakei), which showedpost-harvest dormancy, were collected 30 days after anthesis(DPA 30) and at the mature stage (DPA 60). Poly(A)⁺RNA was extractedfrom the embryos of the seeds and translated in a wheat germsystem. The majority of products of translation from the twogenotypes migrated to the same positions in two-dimensionalgels. Levels of six (for polypeptides h, i, k, m, n, and o)out of 14 Chihoku-specific mRNAs decreased dramatically duringseed maturation, concurrently with the loss of dormancy. Bycontrast, levels of 3 (for polypeptides c, e and f) out of 6Kitakei specific mRNAs were maintained during maturation andduring a 48-h imbibition of the dormant seeds but decreasedat germination. Polypeptides n of Chihoku and e of Kitakei hadthe same molecular size and slightly different pI values. Thesetwo polypeptides may be encoded by the same gene and may playsome role in the maintenance of seed dormancy. Levels of mRNAsfor 10 polypeptides, found in both Chihoku and Kitakei embryosat DPA 30, changed to different extents during maturation. Outof the 10 mRNAs, the relative abundance of 4 mRNAs of Kitakeidid not change dramatically during seed maturation, while inChihoku these mRNAs decreased in level or disappeared duringthe same maturation period. In addition, levels of 2 of these4 mRNAs did not decrease significantly during imbibition ofthe dormant Kitakei seeds but disappeared upon treatment forbreaking of dormancy. The maintenance of these mRNAs in thedormant seeds during maturation and imbibition suggests thatthe respective gene products are involved in the maintenanceof dormancy in wheat seeds. (Received December 5, 1991; Accepted April 1, 1992)