Fig. 5. Expression of GRAM, PROL and AMPHB RNA. In situ hybridisation to detect GRAM (A-C), PROL (D-F) and AmPHB (G-I) RNA. (A,D,G) Longitudinal sections and (B,E,H) transverse sections of wild-type apices; (C,F,I) transverse sections of gram mutant apices. The youngest leaf primordia are towards the centre of each apex. (A) GRAM transcript (detected as a dark precipitate) is abaxially restricted and becomes most abundant in the abaxial margins (B). PROL expression in wild type (D,E) is abaxial in newly initiated primordia (inset in E) and later confined to the developing midveins of leaves. (G,H) Expression of AmPHB RNA is detected within the wild-type SAM and throughout leaf initials within it, becomes restricted to an adaxial region of leaf primordia after initiation then to adaxial leaf margins and to the vasculature of leaves and stem. In gram mutant leaves, GRAM (C) and PROL (F) expression is lost from the marginal, abaxial domain of developing leaves, whereas AmPHB now extends into this region (I).