Qikai Zhang

Coconut (Cocos nucifera L.) is an important tropical horticultural crop valued for its edible endosperm with high oil content. However, the molecular mechanisms governing carbon partitioning and the regulation of glycolytic genes during endosperm development remain largely unclear. Fructose-1,6-bisphosphate aldolase (FBA), a key enzyme in glycolysis, plays a central role in carbohydrate metabolism, yet its transcriptional regulatory mechanisms in coconut have not been elucidated. In this study, the CoFBA promoter (proFBA) was isolated and used for yeast one-hybrid screening, leading to the identification of a GATA transcription factor, CoGATA2. Subcellular localization analysis confirmed that CoGATA2 is localized in the nucleus. Yeast one-hybrid assays, electrophoretic mobility shift assays (EMSA), and transient expression in coconut protoplasts demonstrated that CoGATA2 directly binds to a proFBA fragment containing the predicted GATA motif and represses CoFBA expression. Moreover, virus-induced gene silencing (VIGS) of CoGATA2 in coconut callus resulted in significant upregulation of CoFBA expression and increased fructose-1,6-bisphosphate (FBP) levels. Collectively, these findings demonstrate that CoGATA2 functions as a transcriptional repressor of CoFBA and that this regulation correlates with altered FBP levels in coconut callus. However, the precise mechanism by which FBP accumulation occurs and its relationship to glycolytic flux require further investigation. This study provides new insights into the transcriptional regulation of a key glycolytic gene in coconut and offers a foundation for future efforts to manipulate carbon partitioning in this important horticultural crop.

Somatic embryogenesis (SE)—the reprogramming of somatic cells to follow an embryogenic pathway—remains inefficient in the tropical monocot areca palm (Areca catechu L.) due to poorly understood constraints on cell fate transition. Using single-factor and orthogonal experiments, we investigated how plant growth regulators (PGRs), nitrogen source, and carbon supply regulate the acquisition of embryogenic competence. The optimal condition (Y3 medium + 6-BA + TDZ + 30 g/L sucrose) yielded a somatic embryo induction rate of 48.62%, more than six-fold higher than that of the unoptimized control. Cytologically, embryogenic callus consisted of small, densely cytoplasmic cells with large, centrally positioned nuclei with decondensed chromatin (i.e., loosely packed, transcriptionally active chromatin) and minimal vacuolation—hallmarks of meristematic, embryogenic-competent cells—whereas non-embryogenic callus contained large, highly vacuolated irregular cells. Histological tracking revealed that areca somatic embryos faithfully recapitulate the zygotic developmental program, including bipolarity establishment and procambium differentiation. Mechanistically, we show that the 6-BA + TDZ combination likely acts by inducing endogenous auxin synthesis; moderate ammonium supply (Y3 medium, NO₃⁻/NH₄⁺ ratio 3.6:1) minimizes browning; and 30 g/L sucrose provides optimal energy supply and osmotic regulation. This optimized SE system establishes a tractable model for studying somatic cell reprogramming in a woody monocot.