Abstract
Flowering is of utmost relevance for the agricultural productivity of the sugarcane bioeconomy, but data and knowledge of the genetic mechanisms underlying its photoperiodic induction are still scarce. An understanding of the molecular mechanisms that regulate the transition from vegetative to reproductive growth in sugarcane could provide better control of flowering for breeding. This study aimed to investigate the transcriptome of +1 mature leaves of a sugarcane cultivar subjected to florally inductive and non-inductive photoperiodic treatments to identify gene expression patterns and molecular regulatory modules. We identified 7,083 differentially expressed (DE) genes, of which 5,623 showed significant identity to other plant genes. Functional group analysis showed differential regulation of important metabolic pathways involved in plant development, such as plant hormones (i.e., cytokinin, gibberellin, and abscisic acid), light reactions, and photorespiration. Gene ontology enrichment analysis revealed evidence of upregulated processes and functions related to the response to abiotic stress, photoprotection, photosynthesis, light harvesting, and pigment biosynthesis, whereas important categories related to growth and vegetative development of plants, such as plant organ morphogenesis, shoot system development, macromolecule metabolic process, and lignin biosynthesis, were downregulated. Also, out of 76 sugarcane transcripts considered putative orthologs to flowering genes from other plants (such as Arabidopsis thaliana, Oryza sativa, and Sorghum bicolor), 21 transcripts were DE. Nine DE genes related to flowering and response to photoperiod were analyzed either at mature or spindle leaves at two development stages corresponding to the early stage of induction and inflorescence primordia formation. Finally, we report a set of flowering-induced long non-coding RNAs and describe their level of conservation to other crops, many of which showed expression patterns correlated against those in the functionally grouped gene network.
Highlights
Flowering is an essential part of the life cycle for angiosperms
After 7 months, plants were submitted to two different photoperiod treatments, either a constant long day (LD) photoperiod of 13 h and 30 min for non-inductive photoperiodic treatments (NIPT), or a short day (SD) photoperiodic treatment of 12 h and 50 min shortened by 45 s per day as an inductive photoperiodic treatment (IPT) until inflorescence emergence
We found 7,083 transcripts with statistically significant differentially expressed (DE) comparing induced to non-induced treatments
Summary
Flowering is an essential part of the life cycle for angiosperms. It influences the plant’s adaptation to different environments, vegetative development, biomass accumulation, and grain production (Hill and Li, 2016). Flowering is coordinated by a diversity of genes organized in an intricate network of five gene pathways: photoperiod, vernalization, autonomous, gibberellin, and age (Wellmer and Riechmann, 2010; Srikanth and Schmid, 2011; Yamaguchi and Abe, 2012; Song et al, 2015; Hill and Li, 2016). These pathways, coupled with soil quality, water supply, and temperature, can restrain, promote, or disrupt flowering (Jackson, 2009; Hong and Jackson, 2015; Brambilla et al, 2017). The difficulty of achieving flowering synchronism hampers breeding as sugarcane cultivars show high variability for flowering time (Glassop et al, 2014; Melloni et al, 2015)
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