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Fig. 4. ns transcripts predominately accumulate in tissues enriched for
shoot meristems and young primordia. (A) Schematic drawing of coleoptile
development. The coleoptile (col) emerges from the periphery of the SAM and
grows to form a coleoptilar ring that eventually encloses the SAM. The frame
in the cartoon of the coleoptilar stage embryo on the left indicates the plane
of the transverse section depicted to the right. (B) In situ hybridization of
transverse sections of developing maize embryos reveal that ns
transcripts accumulate in the tips of the emerging coleoptile. (C) Cartoon
depicting a median longitudinal section through the shoot apex of a maize
seedling 14 days after germination. The midrib regions of leaf primordia (C-H)
are designated by plastochron (P) number, such that the incipient primordium
(on the SAM flank) is labeled P0, the next oldest leaf is labeled P1, and so
on. The margins (r) of the corresponding leaf primordia are found on the flank
of the SAM opposing the midrib. Arrows indicate the position of transverse
sections shown in D-F; corresponding close-up images are shown in G-I. (D-I)
In situ hybridization of serial transverse sections reveal that ns
transcripts accumulate in the marginal edges of leaf primordia (r in G-I) and
also in two lateral foci in the founder cells of the new leaf primordium (P1
in D and G). (J) Schematic drawing of maize flower development [based on Cheng
et al. (Cheng et al., 1983)]. Longitudinal (K,M-P) and transverse (L) sections
through female inflorescences or florets at different developmental stages
show ns activity in marginal cells of all floral organs: glumes
(K,L), lemmas (M-O), paleas (K-M), stamens (N-P) and gynoecium (O,P).
Expression of ns in the gynoecium is detected in the gynoecial ridge
(O), a small cleft to the ovule primordium is marked by an asterisk. (K)
Longitudinal section of a female inflorescence. (L) Transverse section of a
spikelet meristem. (M) Longitudinal section of an upper and lower floret
meristem. (N) Longitudinal section of a slightly older flower than that shown
in M. (O) Longitudinal section of an upper flower. (P) Longitudinal section of
a slightly older upper flower than that shown in O. (Q) Schematic drawing of a
longitudinal section through a maize flower, with ns1 expression
domains depicted in red. IM, inflorescence meristem; SPM, spikelet pair
meristem; ig, inner glume; og, outer glume; UFM, upper floret meristem; LFM,
lower floret meristem; il, inner lemma; ol, outer lemma; ip, inner palea; op,
outer palea; gy, gynoecium; st, stamen. Scale bars: 50 µm.
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