Flowering-time genes modulate meristem determinacy and growth form in Arabidopsis thaliana

Abstract

Plants have evolved annual and perennial life forms as alternative strategies to adapt reproduction and survival to environmental constraints. In isolated situations, such as islands, woody perennials have evolved repeatedly from annual ancestors 1 . Although the molecular basis of the rapid evolution of insular woodiness is unknown, the molecular difference between perennials and annuals might be rather small, and a change between these life strategies might not require major genetic innovations 2,3 . Developmental regulators can strongly affect evolutionary variation 4 and genes involved in meristem transitions are good candidates for a switch in growth habit. We found that the MADS box proteins SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1) and FRUITFULL (FUL) not only control flowering time, but also affect determinacy of all meristems. In addition, downregulation of both proteins established phenotypes common to the lifestyle of perennial plants, suggesting their involvement in the prevention of secondary growth and longevity in annual life forms.Plant growth originates from a small number of undifferentiated cells called meristems. Primary meristems are established during embryogenesis and form primary tissues from which all plant organs develop. Secondary meristems, such as axillary meristems and the cambium, originate within primary tissues. Meristems can be determinate-that is, consumed for the formation of an organ-or indeterminate, meaning that they are active throughout the life span of a plant. Upon floral induction in annual plants, vegetative shoot meristems undergo the transition to inflorescence meristems. These inflorescence meristems will remain indeterminate for some time to generate determinate floral meristems giving rise to flowers. Finally, all meristems are consumed and the plants die in the same growing season. In contrast, perennial plants have evolved more elaborate life strategies to survive harsh environmental conditions for many years by forming perennial structures such as overwintering buds, bulbs or tubers, which contain at least one indeterminate meristem for the outgrowth in the next season 2 . Often, perennial plants incorporate enormous amounts of long-lived and eventually dead biomass (wood) through cambial activity (secondary growth).Arabidopsis thaliana is a small annual herb in which floral induction is controlled by different flowering-time pathways. These pathways depend on environmental cues, such as day length (photoperiod) and vernalization (cold temperature), or on plant age. Arabidopsis is a facultative long-day plant that flowers much faster under long (16 h/day) than short (8 h/day) light periods. After perceiving flowering-inducing long days, the key regulator of the photoperiodic pathway, CONSTANS (CO), activates FT (FLOWERING LOCUS T) in the leaf vasculature. The FT protein is transported to apical meristems, where it triggers the floral transition 5 . SOC1 (AGL20) and FUL (AGL8) are MADS box genes acting downstream of FT in apical meristems, but they are ...

Contributions of Flowering Time Genes to Sunflower Domestication and Improvement

“…QTLs for additional vegetative and reproductive traits map to this locus in multiple crosses Wills and Burke 2007;, and NILs segregating for the locus show genotype-dependent differences in some of these traits (Blackman et al 2010). Genetic evidence supports roles for FT in plant architecture, meristem size, leaf development, and abscission zone formation in Arabidopsis and tomato ( Jeong and Clark 2005;Jeong et al 2008;Melzer et al 2008;Shalit et al 2009;Krieger et al 2010).…”

Helianthus winteri (Asteraceae), a New Perennial Species From the Southern Sierra Nevada Foothills, California

“…Evolution of woody taxa from herbaceous progenitors is well established (e.g., Bö hle et al 1996;Ballard and Sytsma 2000), and such a transformation may occur relatively rapidly with minimal genetic change (Thomas et al Groover 2005), such that the genetic distinction between H. winteri and H. annuus may be subtle. Molecular studies suggest that the development of woody characteristics may be linked to the timing of flowering (Melzer et al 2008;Lens et al 2012). Field observations of first-year plants of H. winteri and H. annuus reveal relatively few clear morphological differences; however, differences in vascular differentiation has been observed as early as three weeks postgermination (Moyers and Rieseberg 2013).…”

Extended Vernalization Regulates Inflorescence Fate in Arabis alpina by Stably Silencing PERPETUAL FLOWERING1

“…Previous studies in A. thaliana suggested that FT, which is a target of FLC, is involved in memory of 269 floral commitment (Melzer et al, 2008;Liu et al, 2014;Müller-Xing et al, 2014). Therefore, we 270 compared the expression of the A. alpina FT homolog, AaFT1 (Adrian et al, 2010), in shoot apices 271 after different periods of vernalization.…”