DELAY OF GERMINATION 1‐LIKE 4 acts as an inducer of seed reserve accumulation

Summary More than 70% of global food supply depends on seeds. The major seed reserves, such as proteins, lipids, and polysaccharides, are produced during seed maturation. Here, we report that DELAY OF GERMINATION 1‐LIKE 4 (DOGL4) is a major inducer of reserve accumulation during seed maturation. The DOGL family proteins are plant‐specific proteins of largely unknown biochemical function. DOGL4 shares only limited homology in amino acid sequence with DOG1, a major regulator of seed dormancy. DOGL4 was identified as one of the outstanding abscisic acid (ABA)‐induced genes in our RNA sequencing analysis, whereas DOG1 was not induced by ABA. Induction of DOGL4 caused the expression of 70 seed maturation‐specific genes, even in germinating seeds, including the major seed reserves ALBUMIN, CRUCIFERIN and OLEOSIN. Although DOG1 affects the expression of many seed maturation genes, the major seed reserve genes induced by DOGL4 are not altered by the dog1 mutation. Furthermore, the reduced dormancy and longevity phenotypes observed in the dog1 seeds were not observed in the dogl4 mutants, suggesting that these two genes have limited functional overlap. Taken together, these results suggest that DOGL4 is a central factor mediating reserve accumulation in seeds, and that the two DOG1 family proteins have diverged over the course of evolution into independent regulators of seed maturation, but retain some overlapping function. Significance Statement This study revealed the function of DOGL4 as an inducer of seed reserve accumulation, which is distinct from the major function of DOG1 in dormancy. These diverged functions of the DOG1 family proteins and their overlapping roles in the regulation of some seed maturation genes, which were also suggested from this study, provide significant insights into the evolution of seed maturation, dormancy and other programs that are critical for understanding how seed plants have emerged.