Abstract
After domestication in the Near East around 10,000 years ago several founder crops, flax included, spread to European latitudes. On reaching northerly latitudes the architecture of domesticated flax became more suitable to fiber production over oil, with longer stems, smaller seeds and fewer axillary branches. Latitudinal adaptations in crops typically result in changes in flowering time, often involving the PEBP family of genes that also have the potential to influence plant architecture. Two PEBP family genes in the flax genome, LuTFL1 and LuTFL2, vary in wild and cultivated flax over latitudinal range with cultivated flax receiving LuTFL1 alleles from northerly wild flax populations. Compared to a background of population structure of flaxes over latitude, the LuTFL1 alleles display a level of differentiation that is consistent with selection for an allele III in the north. We demonstrate through heterologous expression in Arabidopsis thaliana that LuTFL1 is a functional homolog of TFL1 in A. thaliana capable of changing both flowering time and plant architecture. We conclude that specialized fiber flax types could have formed as a consequence of a natural adaptation of cultivated flax to higher latitudes.
Highlights
Crop plants were domesticated in the late Pleistocene to early Holocene at multiple centers around the world and many of them subsequently expanded northwards after glacial retreat[1]
In Arabidopsis thaliana, plant architecture can be modified simultaneously with both flowering time by changes in regulation of the FT and TFL1 genes[26], which belong to the phosphatidyl ethanolamine-binding protein (PEBP) family[27] and control plant development through regulation of floral meristem initiation
PEBP orthologs in flax and the diversity at LuTFL1 locus
Summary
Crop plants were domesticated in the late Pleistocene to early Holocene at multiple centers around the world and many of them subsequently expanded northwards after glacial retreat[1]. Plants of Neolithic Package, adapted to Near Eastern conditions, are often long-day and vernalization dependent for flowering. Those crops would have struggled in short growing season in Europe. The orthologs of FT and TFL1 in tomato have a strong effect on tomato fruit weight and number[29], plant architecture and height, and flowering time[30,31] Such differences in fruit weight and plant stature underlie the distinction between fiber and oil specialized varieties in flax, raising the possibility that the PEBP gene family in flax could be associated with both architectural changes and adaptation to northerly latitudes through modifying flowering time. We validated the effect of a gene candidate for selection, LuFTL1 on plant architecture and flowering time through heterologous expression in Arabidopsis thaliana
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