The maize pentatricopeptide repeat gene empty pericarp4 (emp4) is required for proper cellular development in vegetative tissues

• Published in: Plant science (Limerick) 2014-06, Vol.223, p.25-35
• Main Authors: Gabotti, Damiano, Caporali, Elisabetta, Manzotti, Priscilla, Persico, Martina, Vigani, Gianpiero, Consonni, Gabriella
• Format: Article
• Language: English
• Subjects: Cell Proliferation - radiation effects; Cell Respiration - radiation effects; Cell Shape - radiation effects; Empty pericarp mutants; Gene Deletion; Genes, Plant; Germination - radiation effects; Leaf cell ultra-structure; Light; Mitochondria; Mitochondria - metabolism; Mutation - genetics; Organ Specificity - genetics; Organ Specificity - radiation effects; Oxygen - metabolism; Pentatricopeptide repeat proteins; Phenotype; Plant Cells - radiation effects; Plant Cells - ultrastructure; Plant Leaves - cytology; Plant Leaves - radiation effects; Plant Leaves - ultrastructure; Plant Proteins - chemistry; Plant Proteins - genetics; Plant Proteins - metabolism; Repetitive Sequences, Amino Acid; Seedlings - growth & development; Seedlings - radiation effects; Subcellular Fractions - metabolism; Zea mays; Zea mays - cytology; Zea mays - genetics; Zea mays - radiation effects; Zea mays - ultrastructure
• ISSN: 0168-9452; 1873-2259
• DOI: 10.1016/j.plantsci.2014.02.012

•The effect of a mutation in the emp4 PPR gene on seedling development was analyzed.•We compare mutant and wild-type cellular ultrastructure and function of organelles.•Main defects were presence of empty cells or cells with poorly developed organelles.•Mutant chloroplasts are reminiscent of senescent organelles.•Damages were more severe in light-grown than in dark-grown mutant tissues. The empty pericarp4 (emp4) gene encodes a mitochondrion-targeted pentatricopeptide repeat (ppr) protein that is involved in the regulation of mitochondrial gene expression and is required for seed development. In homozygous mutant emp4-1 kernels the endosperm is drastically reduced and the embryo is retarded in its development and unable to germinate. With the aim of investigating the role of emp4 during post-germinative development, homozygous mutant seedlings were obtained by cultivation of excised immature embryos on a synthetic medium. In the mutants both germination frequency as well as the proportion of seedlings reaching the first and second leaf stages were reduced. The anatomy of the leaf blades and the root cortex was not affected by the mutation, however severe alterations such as the presence of empty cells or cells containing poorly organized organelles, were observed. Moreover both mitochondria and chloroplast functionality was impaired in the mutants. Our hypothesis is that mitochondrial impairment, the primary effect of the mutation, causes secondary effects on the development of other cellular organelles. Ultra-structural features of mutant leaf blade mesophyll cells are reminiscent of cells undergoing senescence. Interestingly, both structural and functional damage was less severe in seedlings grown in total darkness compared with those exposed to light, thus suggesting that the effects of the mutation are enhanced by the presence of light.