Mj. Muhitch et al., IMMUNOLOCALIZATION OF A UNIQUE FORM OF MAIZE KERNEL GLUTAMINE-SYNTHETASE USING A MONOCLONAL-ANTIBODY, Plant physiology, 107(3), 1995, pp. 757-763
The pedicel (basal maternal tissue) of maize (Zea mays L.) kernels con
tains a physically and kinetically unique form of glutamine synthetase
(GS(p1)) that is involved in the conversion of transport forms of nit
rogen into glutamine for uptake by the developing endosperm (M.J. Muhi
tch [1989] Plant Physiol 91: 868-875). A monoclonal antibody has been
raised against this kernel-specific GS that does not cross-react eithe
r with a second GS isozyme found in the pedicel or with the GS isozyme
s from the embryo, roots, or leaves. When used as a probe for tissue p
rinting, the antibody labeled the pedicel tissue uniformly and also la
beled some of the pericarp surrounding the lower endosperm. Silver-enh
anced immunogold staining of whole-kernel paraffin sections revealed t
he presence of GS(p1) in both the vascular tissue that terminates in t
he pedicel and the pedicel parenchyma cells, which are located between
the vascular tissue and the basal endosperm transfer cells. Light sta
ining of the subaleurone was also noted. The tissue-specific localizat
ion of GS(p1) within the pedicel is consistent with its role in the me
tabolism of nitrogenous transport compounds as they are unloaded from
the phloem.