Crosstalk in the darkness: bulb vernalization activates meristem transition via circadian rhythm and photoperiodic pathway

Abstract

Background: Geophytes possess specialized storage organs -bulbs, tubers, corms or rhizomes, which allow their survival during unfovarable periods and provide energy support for sprouting and sexual and vegetative reproduction. Bulbing and flowering of the geophyte depend on the combined effects of the internal and external factors, especially temperature and photoperiod. Many geophytes are extensively used in agriculture, but mechanisms of regulation of their flowering and bulbing are still unclear. Results: Comparative morpho-physiological and transcriptome analyses and quantitative validation of gene expression shed light on the molecular regulation of the responses to vernalization in garlic, a typical bulbous plant. Long dark cold exposure of bulbs is a major cue for flowering and bulbing, and its interactions with the genetic makeup of the individual plant dictate the phenotypic expression during growth stage. Photoperiod signal is not involved in the initial nuclear and metabolic processes, but might play role in the later stages of development, flower stem elongation and bulbing. Vernalization for 12 weeks at 4°C and planting in November resulted in flower initiation under short photoperiod in December-January, and early blooming and bulbing. In contrast, non-vernalized plants did not undergo meristem transition. Comparisons between vernalized and non-vernalized bulbs revealed~14,000 differentially expressed genes.Conclusions: Low temperatures stimulate a large cascades of molecular mechanisms in garlic, and a variety of flowering pathways operate together for the benefit of meristem transition, annual life cycle and viable reproduction results.The circadian clock appears to play a central role in the transition of the meristem from vegetative to reproductive stage in bulbous plant, serving as integrator of the low-temperature signals and the expression of the genes associated with vernalization, photoperiod and meristem transition. The reserved photoperiodic pathway is integrated at an upstream point, possibly by the same receptors. Therefore, in bulb, low temperatures stimulate cascades of developmental mechanisms, and several genetic flowering pathways intermix to achieve successful sexual and vegetative reproduction.

Large-scale analyses of angiosperm Flowering Locus T genes reveal duplication and functional divergence in monocots

“…Vernalization and non-vernalization RNA-seq data were downloaded from NCBI; Aquilegia coerulea was vernalized at 6°C ( Sharma et al., 2019 ), Allium sativum vernalized at 4°C ( Ben Michael et al., 2020 ), Arabidopsis thaliana vernalized at 4°C ( Xi et al., 2010 ), Brachypodium distachyon vernalized at 5°C ( Ream et al., 2014 ), Brassica rapa vernalized at 5°C ( Jung et al., 2018 ), Camelina sativa ( ), Brassica napus vernalized at 5°C ( Jones et al., 2018 ), Dactylis glomerata vernalized in natural environmental conditions ( Feng et al., 2018 ), Hordeum vulgare ( Deng et al., 2015 ), Mimulus guttatus vernalized at 4°C ( Preston et al., 2016 ), and Triticum aestivum ( ). Reads were mapped to the reference genome using Hisat2 v2.0.1 ( Kim et al., 2015 ) then assembled and quantified using StringTie v1.2.2 software ( Pertea et al., 2015 ).…”

Assessment of interspecific hybridization between wild beet Beta vulgaris L. subsp. maritima and cultivated sugar beet under Moroccan conditions

“…Vernalization requirement appears to be strongly related to temperature (Limin and Fowler, 2006), geographical latitudinal gradients (Boudry et al, 2002;Rhoné et al, 2008), and photoperiod and cold treatment (Michael et al, 2020).…”

Genomic Survey of PEBP Gene Family in Rice: Identification, Phylogenetic Analysis, and Expression Profiles in Organs and under Abiotic Stresses

“…In plants, PEBP family is involved in flowering time control, seed dormancy, plant architecture determination, tuber formation, and sink-source allocation [12][13][14][15][16][17]. PEBP proteins act as key factors to regulate vegetative to reproductive phase transition or floral transition in plants [18][19][20][21].…”