Humulus lupulus Transcriptome or Gene expression. Humulus lupulus

Transcriptional profiling of hop samples throughout in vitro culture on medium with sucrose and hormones IAA and BAP Study of gene expression involved in stress response during in vitro culture and in organogenic nodule formation Hop (Humulus lupulus L.) is an economically important plant forming organogenic nodules which can be used for genetic transformation and micropropagation. We are interested in the mechanisms underlying reprogramming of cells through stress and hormone treatments. To investigate the spatio-temporal sequence of events that underlies competence acquisition for organogenesis three main stages were selected: (i) internodes at the time of excision from the parent plant (T0); (ii) internodes grown for 15 days on culture medium in which several prenodular structures are formed inside the calli (T15d); and (iii) nodule forming tissue after 28 days of culture (T28d). Additionally a control was included corresponding to 28 days of culture without hormones, lacking nodule formation and plantlet regeneration abilities, in order to identify genes specifically involved in morphogenesis (T28dWH). Organogenic nodule formation is a morphogenic process that shares features with somatic embryogenesis though in the former no shoot/root pole is established and plantlet regeneration can occur from different peripheral regions of nodules. Previous studies have shown that the organogenesis-determining period (when cells are determined to form nodules) occurs in between 15 and 25 days of culture corresponding to prenodular and first nodular stages. When nodules are fully developed they are surrounded by layers of elongated, highly vacuolated cells that may degenerate when nodules start differentiating plantlets. Plantlet regeneration from organogenic nodules can be observed after 45 days of culture. However, organogenic nodules after 28 days of culture are already determined to undergo plantlet regeneration, since they no longer require exogenous supply of hormones. Explants cultured in medium without hormones can develop incipient prenodular structures with vascular tissue but not nodules, thus lacking morphogenic potential. Keywords: Plant development, Time course Overall design: 3 time points: 3 Biological replicates and 1 technical replicate (1 dye-swap). 1 control at beginning of culture and 1 control wihout hormones. One replicate per array. Each clone printed twice in the same sub-grid