PpCESA5 alone sustains gametophore morphogenesis in the absence of other PpCESAs. In contrast to WT (A) and ppcesa5KO, which produces no leafy gametophores (B) and ppcesa4/6/7/10KO, which produces normal leafy gametophores (C), four independent ppcesa6/7/3/8/10/4KO lines produce colonies with stunted leafy gametophores (D–G, white arrow heads). Constitutive expression of PpCESA5 in ppcesa6/7/3/8/10/4KO-41 restored normal gametophore morphology (H). PpCESA5pro:mEGFP-PpCESA5 is expressed in the gametophore shoot apical meristems (I) and in gametophore buds before (J) and after (K) initiation of the first leaves. Scale bar in A refers to B–H and scale bar in J refers to K.