Phosphatidylserine decarboxylases (PSDs) catalyze the production of phosphatidylethanolamine (PE) from phosphatidylserine (PS) and are crucial for the maintenance of PE levels in fungi. The PSDs are classified into two types; the type I PSDs are conserved from bacteria to humans, while the type II PSDs exist only in fungi and plants. In yeasts, the deletion of type I PSD-encoding genes causes severe growth retardation. In contrast, the deletion of type II PSD-encoding genes has little or no effect. In this study, we found four genes encoding type II PSD orthologs in the filamentous fungus Aspergillus nidulans; these included psdB, psdC, psdD, and psdE. Deletion of psdB caused severe growth defects on minimal medium and these defects were partially restored by the addition of ethanolamine, choline, PE, or phosphatidylcholine into the medium. The conidiation efficiency of the psdB deletion mutant was dramatically decreased and its conidiophore structures were aberrant. In the psdB deletion mutant, the PE content decreased while the PS content increased. We further showed that PsdB had a major PSD activity. Our findings suggest that the type II PSDs exert important roles in the phospholipid homeostasis, and in the growth and morphogenesis of filamentous fungi.

磷脂酰丝氨酸脱羧酶（PSDs）催化磷脂酰丝氨酸（PS）生成磷脂酰乙醇胺（PE），对于维持真菌中PE的含量至关重要。PSD分为两种类型：I型PSD从细菌到人类都是保守的，而II型PSD仅存在于真菌和植物中。在酵母中，I型PSD编码基因的缺失导致严重的生长迟缓。相反，II型PSD编码基因的缺失几乎没有影响。在这项研究中，我们在丝状真菌构巢曲霉中发现了四个编码II型PSD直系同源基因的基因。这些包括psdB，psdC，psdD和psdE。删除psdB在基本培养基上引起严重的生长缺陷，通过向培养基中添加乙醇胺，胆碱，PE或磷脂酰胆碱可部分修复这些缺陷。psdB缺失突变体的分生效率大大降低，其分生孢子结构异常。在psdB缺失突变体中，PE含量降低而PS含量升高。我们进一步表明PsdB具有主要的PSD活性。我们的发现表明II型PSD在磷脂稳态，丝状真菌的生长和形态发生中起重要作用。