Ya Liu, Ruoman Wang, Shuya Wang, Tongtong Wang, Jinwei Suo, Jingwei Yan, Jiasheng Wu
Reproduction is essential for seed plant survival, and in gymnosperms, cone enlargement plays a pivotal role in seed production and reproduction. However, the molecular mechanisms regulating cone enlargement after fertilization remain poorly understood. Here, using Torreya grandis, a representative gymnosperm species with persistently low cone enlargement efficiency, we elucidated the molecular regulation of cone enlargement and identified sucrose non-fermenting 1-related protein kinase 1 (TgSnRK1) as a novel negative regulator of this process. TgSnRK1 physically interacted with the WRKY transcription factor TgWRKY47 both in vitro and in vivo. Functional analyses revealed that TgSnRK1 acted upstream of TgWRKY47 and suppressed cone enlargement in T. grandis. Phosphorylation assays revealed that TgSnRK1 directly phosphorylated TgWRKY47 at Thr-75. This phosphorylation event markedly reduced the transactivation activity of TgWRKY47, thereby attenuating its activation of the cell wall-remodeling gene TgEXPA2, a key regulator of cell expansion during cone enlargement. Together, these findings establish a phosphorylation-dependent TgSnRK1-TgWRKY47-TgEXPA2 regulatory pathway in which developmental attenuation of TgSnRK1-mediated phosphorylation of TgWRKY47 at Thr-75 enhances TgWRKY47 transactivation activity, thereby promoting TgEXPA2-dependent cone enlargement. This study advances our understanding of reproductive development in gymnosperms and identifies potential molecular targets for improving reproductive efficiency and seed yield.