Phenotypic, bioinformatics and molecular analyses related to the development and reproductive transition of Humulus lupulus l. (Hop) in subtropical regions of Brazil

Abstract

Plants have evolved to perceive endogenous and environmental signals to better adjust their phenological cycle, increasing the chance of reproductive success. These processes vary considerably between plants from different regions subject to variable climatic conditions. With the aim to establish the hop culture in subtropical regions of Brazil, it is indispensable to understand the plant development and plasticity in response to environmental changes and determine the factors that dictate the floral transition. To achieve this goal, first we performed a review (first chapter) and then two experimental works. In the first, we study the hop phenology subjected to Brazilian conditions and focusing on the floral transition. In detail, we analyzed the growth pattern and some environmental cues and related these data to the expression pattern of microRNAs 156/172 during the development. The phenotypic evaluations (number of nodes, heteroblasty, flowers) were followed by a decrease of miR156 expression levels and increase of miR172 levels. This suggested that the flowering in hop plants subjected to subtropical Brazilian conditions but irrigated is dependent on the age and can occur at any time of year. In the second work, since MADS-box is an important family of transcription factors involved in many aspects of plant development, we performed a genome-wide and transcriptional analysis. We found 65 MADS-box genes in the hop genome being them classified into 11 subfamilies within type II group (MIKCc) and in three subfamilies of type I. In the MIKCC group, we did not find members of the FLC and AGL17 subfamilies, involved in flowering repression and activation, respectively. FLC is related to vernalization thus, these results together with the fact that hop bloomed in our experiments suggest that cold periods are not necessary for hop flowering, whereas other floral activators than AGL17 are able

to promote phase transition. The presence and expression profile of A-class, B-class, C/D-class, and E- class genes allowed us to propose how these influence the hop floral architecture. Moreover, it was

identified a MADS-box gene expressed exclusively in the lupulin glands and involved in the secondary metabolism in the lupulin glands. Thus, our work contributes to understanding hop development and molecular aspects related to floral transition open perspectives to breeding programs and cultivation in different regions than temperate zones.