Author/Editor		Kladnik, Aleš; Chamusco, Karen; Dermastia, Marina; Chourey, Prem
Title		Evidence of programmed cell death in post-phloem transport cells of the maternal pedicel tissue in developing caryopsis of maize
Type		članek
Source		Plant Physiol
Vol. and No.		Letnik 136
Publication year		2004
Volume		str. 3572-81
Language		eng
Abstract		We present cellular- and ultracellular-level studies here to show developmental programmed cell death (PCD) of placentochalazal (P-C) cell layers in maternal pedicel tissue in developing caryopses of normal seed (Mnl) and in the invertasedeficient mininlure (mnl) seed mutant in maize (Zen mays). PCD was evidenced by loss of nuclei and all subcellalar membranous organizations in many P-C layers. The terminal deoxynucleotidyl transferase-mediated X-dUTP nick-end labeling (TUNEL) stain that is diagnostic of apoptotic-like PCD identified spatially and temporally two distinctive subdomains, which coincided with nucellar and integumental P-C layers based on their developmental origins. The early phase of PCD in the nucellar P-C was TUNEL negative and was specific to only the fertilized caryopses, indicating that the signaling for PCD in these maternal cells originated in the zygotic tissues. In Eact, the initiation of PCD coincided with endosperm cellularization and was rapidly and coordinately completed prior to the beginning of the major storage phase in endosperm. Cell shape in these cell layers was also influenced by the genotype of Hlial endosperm. The later phase of PCD was restricted to the integumental P-C layers underneath the nucellar cells and was TUNEL positive in both genotypes. The two subdomains of the P-C layers were also distinguishable by unique cell wall-associated phenolic compounds. Based on collective evidence, we infer that the nucellar PCD may have osmolytic etiology and may lead to activation of the post-phloem transport function of the P-C layer, whereas the integumental PCD was senescent related, in particular, protecting the maturing seed against microbes that may be transported from the maternal tissue.
Descriptors		CORN SEEDS APOPTOSIS MUTATION GENOTYPE PHENOTYPE DNA FRAGMENTATION MICROSCOPY, ELECTRON