Seasonal behavior is important for fitness in temperate environments but it is unclear how progeny gain their initial seasonal entrainment. Plants use temperature signals to measure time of year, and changes to life histories are therefore an important consequence of climate change. Here we show that in Arabidopsis the current and prior temperature experience of the mother plant is used to control germination of progeny seeds, via the activation of the florigen Flowering Locus T (FT) in fruit tissues. We demonstrate that maternal past and current temperature experience are transduced to the FT locus in silique phloem. In turn, FT controls seed dormancy through inhibition of proanthocyanidin synthesis in fruits, resulting in altered seed coat tannin content. Our data reveal that maternal temperature history is integrated through FT in the fruit to generate a metabolic signal that entrains the behavior of progeny seeds according to time of year.M any organisms use annual changes in temperature to control their phenology, resulting in predictable timing of key life history events, such as flowering, spawning, and migration (1-3). Understanding crop and ecosystem response to climate change requires knowledge of the temperature control of key developmental transitions, but how new generations achieve seasonal orientation is currently unclear. Seed germination is the first step in plant life history and therefore plays a central role in the control of plant phenology (4) and is extremely sensitive to environmental temperature (3-5). Seed dormancy is established during seed maturation and is imposed by control of hormone signaling and the action of the maternal seed coat. Nearly 30 y ago it was found that environmental signaling throughout the whole maternal life history can affect seed dormancy control in wild oats, and that temperature experience in the vegetative phase before flowering affected progeny seed dormancy (6). Here we show that this response is conserved on the model species Arabidopsis. Our data show that fruit tissues carry a memory of past temperature experience and that flowering pathways control a transgenerational metabolic signal of maternal past temperature experience, which modulates progeny dormancy according to time of year.To test whether past parental temperature experience affected progeny dormancy in the model species Arabidopsis thaliana, we grew plants until the first sign of flowering at either 22°C or 16°C and then placed plants side by side to set seed at 22°C in long days (LDs) (Fig. 1A). We found that in Landsberg erecta (Ler) lower temperature during the vegetative phase caused a large increase in the dormancy of seeds produced later on the plants (Fig. 1A). Lower temperatures during seed set also increase progeny dormancy (6), but we observed no effect of photoperiod on dormancy either before or after flowering, as has been reported previously (7, 8). Therefore, temperature signals before seed fertilization are remembered by the parent plant and used to control offspring behavior.P...

The root stem cell niche defines the area that specifies and maintains the stem cells and is essential for the maintenance of root growth. Here, we characterize and examine the functional role of a quiescent center (QC)-expressed RAC/ROP GTPase activator, RopGEF7, in Arabidopsis thaliana. We show that RopGEF7 interacts with At RAC1 and overexpression of a C-terminally truncated constitutively active RopGEF7 (RopGEF7DC) activates RAC/ROP GTPases. Knockdown of RopGEF7 by RNA interference causes defects in embryo patterning and maintenance of the QC and leads to postembryonic loss of root stem cell population. Gene expression studies indicate that RopGEF7 is required for root meristem maintenance as it regulates the expression of PLETHORA1 (PLT1) and PLT2, which are key transcription factors that mediate the patterning of the root stem cell niche. Genetic analyses show that RopGEF7 interacts with PLT genes to regulate QC maintenance. Moreover, RopGEF7 is induced transcriptionally by auxin while its function is required for the expression of the auxin efflux protein PIN1 and maintenance of normal auxin maxima in embryos and seedling roots. These results suggest that RopGEF7 may integrate auxin-derived positional information in a feed-forward mechanism, regulating PLT transcription factors and thereby controlling the maintenance of root stem cell niches.

Plants integrate seasonal signals, including temperature and day length, to optimize the timing of developmental transitions. Seasonal sensing requires the activity of two proteins, FLOWERING LOCUS C (FLC) and FLOWERING LOCUS T (FT), that control certain developmental transitions in plants. During reproductive development, the mother plant uses FLC and FT to modulate progeny seed dormancy in response to temperature. We found that for regulation of seed dormancy, and function in opposite configuration to how those same genes control time to flowering. For seed dormancy, FT regulates seed dormancy through gene expression and regulates chromatin state by activating antisense transcription. Thus, in the same genes controlled in opposite format regulate flowering time and seed dormancy in response to the temperature changes that characterize seasons.

SummarySeed dormancy is a widespread and key adaptive trait that is essential for the establishment of soil seed banks and prevention of pre‐harvest sprouting. Herein we demonstrate that the endosperm‐expressed transcription factors ZHOUPI (ZOU) and INDUCER OF CBF EXPRESSION1 (ICE1) play a role in determining the depth of primary dormancy in Arabidopsis. We show that ice1 or zou increases seed dormancy and the double mutant has an additive phenotype. This increased dormancy is associated with increased ABA levels, and can be separated genetically from any role in endosperm maturation because loss of ABA biosynthesis or DELAY OF GERMINATION 1 reverses the dormancy phenotype without affecting the aberrant seed morphology. Consistent with these results, ice1 endosperms had an increased capacity for preventing embryo greening, a phenotype previously associated with an increase in endospermic ABA levels. Although ice1 changes the expression of many genes, including some in ABA biosynthesis, catabolism and/or signalling, only ABA INSENSITIVE 3 is significantly misregulated in ice1 mutants. We also demonstrate that ICE1 binds to and inhibits expression of ABA INSENSITIVE 3. Our data demonstrate that Arabidopsis ICE1 and ZOU determine the depth of primary dormancy during maturation independently of their effect on endosperm development.