(Labex Agro:ANR-10-LABX-0001-01)) » SHORT TITLE: FLORIMAIZE « Role of florigen proteins in maize developmental reprogramming under drought stress » Project leaders: Lucio Conti University Of Milan Lucio.Conti@unimi.it François Tardieu INRA, LEPSE francois.tardieu@supagro.inra.fr Context : When to flower is a key decision for plants, affecting the adaptability of species to any given environment. Modulation of flowering (related to the duration of vegetative growth) has been and (still is) a key trait to improve yield in crops, including maize. Objectives : The objective of FLORIMAIZE is to identify the role of the florigen genes (ZCN8 and related genes) in the genetic variability of growth maintenance in maize (parent lines) to identify and develop novel maize phenotype. The project is closely related with DROPS project which analyses the same factors on F1 hybrids Actions planned : Identifying QTLs affecting growth, transpiration and water use Efficiency Identifying eQTLs of ZCN8 and related genes in the same panel of lines ZCN8 eQTLs analysis and molecular dissection eQTLs X QTLs analysis Main results : We have successfully conducted two platform and two field experiments utilising a Maize panel which comprises a large genetic diversity. In Kenya we were able to perform a small scale field experiment comprising 81 lines (including local varieties) grown under different watering scenarios. Several phenotypic traits were captured throughout our experiments. Plant phenology and architecture traits were : Anthesis, Silking, Ear Leaf Dimension and Position, plant height and Total Leaf number. Plant physiological traits included leaf growth, transpiration and water use efficiency. A new workflow for GWAS analysis has been developed, which allowed us to carry out QTLs detection on the whole panel for all the phenotypic and molecular traits. Inclusion of GBS data on an extended panel and following global diversity analysis and imputation were achieved by INRA LeMoulon, thereby increasing the number of markers to 853K SNPs. Alongside phenological data, expression studies allowed us to precisely measure variations in gene expression for the florigen genes ZCN7, ZCN8, ZCN12 (structurally related to each other) and their putative activator ZmCO. This analysis was carried out at three different developmental stages in two independent experiment, totaling nearly 5000 RNA samples. We could detect a clear correlation between expression of the florigen genes and flowering time in Maize. This correlation is reproducible in different conditions (platform and fields). The ZCN genes are controlled by different eQTLs, some of which co-localise with flowering time QTLs in the field. Therefore we were able to link variations in gene expression to physiological traits. Interestingly, we revealed a connection between two florigen genes ZCN8 and ZCN12 whereby these genes share a common mode of regulation. We detected allelic diversity at the ZCN12 locus and related it to ZCN12 expression levels and flowering time. We hypothesize that allelic selection at different florigen genes has played a role in adjusting flowering according to different agricultural scenarios. Partner(s) : James Karanja (KALRO, Kenya) Alain Charcosset (INRA, LeMoulon, FR) Duration : 3 YEARS Budget : 423.072 € This project is supported by Fondazione Cariplo (ref 2013-XXXX) and Agropolis Fondation (reference 1301-010 through the « Investissements d’avenir » programme (Labex Agro:ANR-10-LABX-0001-01)) »