"Secrets of new life's beginnings" "DNA synthesis and metabolic activity in different parts of germinating crop seeds" Monika Rewers, Elwira Śliwińska University of Technology and Life Sciences in Bydgoszcz, Faculty of Agriculture and Biotechnology, Department of Plant Genetics, Physiology and Biotechnology, al. Kaliskiego 7, 85-789 Bydgoszcz e-mail: mrewers@utp.edu.pl Swan - a young seedling of cress (Lepidium sativus); 2014 Moonscape - an embryo of bean (Phaseolus vulgaris); 2014 Tick-Tack-Toe - a pod of broad bean(Vicia faba var. minor); 2014 Sleeping life - an embryo of lentil (Lens culinaris); 2014 Curved - an embryo of pepper (Capsicum annuum); 2014

Description popularizing the research project

What really works on people's imagination are things veiled in mystery. Such a mystery you even cannot steal one glimpse of, as it hides something very important. The most intriguing secrets are the ones which bring dire consequences for those who disclose it out of insatiable curiosity. That was the fate of Orpheus who, although said not to, looked back and lost his Eurydice forever; Pandora, who looked into the forbidden box with consequences for herself and all the humanity; or Hans Dumm, who was turned into stone for the same offence as Orpheus. It is harder to find in the realm of myths and fairy tales an example of a secret which once disclosed will be gone forever.
Nature hides such a secret, a secret which actually does not exist yet. It is hidden deep in thick, hard shells of nuts and seeds. There, comfortable and safe a plant develops. In a cosy seed the cells of its tiny embryo take the roles of particular tissues and organs. Various genes wake up and go dormant, the DNA replicates at a breathtaking rate. Rigid seed coat protects the vulnerable structure of the embryo until it is big and strong enough to germinate and survive the first difficult moments of independent life.
Just as many plant species there are on Earth there are that many details differing their embryogenesis. To discover the secrets, find the differences describe changes and present the milestone moments in development we have to disturb the peace and quiet beneath the seed coats and extract the developing embryo. Often it is not able to continue its growth, however, even a glimpse of the secrets or a shard of knowledge revealed then may bring discoveries of great importance, from storing seeds to finding a variety which will be able to feed growing population of our planet. The secret will be revealed at a cost of hampering or stopping the development of several seeds, yet the results may ease at least a few of the worries freed from Pandora's box: malnutrition, poverty and hunger.

Abstract

One of the essential cellular events of germination is elongation of the cells, which results in the radicle protrusion. Cell elongation is associated with endoreduplication during which DNA synthesis occurs, without subsequent cell division, and thus cells contain amplified DNA content. As with the increase in the DNA content the size of the nucleus and the cell increases, the analysis of DNA synthesis intensity provides information on the region of the embryo where cells elongate. Since the radicle is a first structure that emerges from the seed, it has been widely assumed to be the structure which elongates during germination. Basing on this assumption, mainly radicle or the whole embryonic axis have been used for research on germination. The aim of the project was to determine the regions of the embryo most actively synthesizing DNA during germination of seeds of different types (endospermic, non-endospermic, perispermic, with epigeal or hypogeal seedling growth). Cytometric analyses of different regions of the embryo during germination revealed that depending on the type of seedling growth, endoreduplication intensity is usually the highest in the transition zone between the radicle and hypocotyl (species with an epigeal seedling growth) or in hypocotyl (species with an hypogeal seedling growth). The endopolyploidy level in cotyledons depends on the type of the cotyledons, and it is higher in species with storage cotyledons, than in those which serve as a photosensitizing organ. During germination, the accumulation of the reactive oxygen species (ROS) occurs in the radicle and after radicle protrusion also in the transition zone. It suggests a role of ROS in the protection of the embryo and young seedling against environmental stress factors, however not in the control of cell elongation. Selection of the proper material is particularly important in the expensive molecular studies of germination and in monitoring seed priming procedures. The research was supported by Polish National Science Centre (DEC-2011/03/N/NZ9/03798).

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