Cotyledons contribute to plant growth and hybrid vigor in Arabidopsis
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In hybrids of Arabidopsis, cotyledons influence the amount and proportion of hybrid vigor in total plant growth.
We found Arabidopsis cotyledons are essential for plant growth and in some hybrids for hybrid vigor. In hybrids between C24 and Landsberg erecta (Ler), biomass vigor (heterosis) occurs in the first few days after sowing (DAS), with hybrid cotyledons being larger than those of their parents. C24xLer hybrids are ahead of their parents in activating photosynthesis and auxin pathway genes in cotyledons at 3–4 DAS. “Earliness” is also present in newly emerged C24xLer hybrid leaves. We showed cotyledon removal at 4 DAS caused significant biomass reduction in later growth in hybrids and parental lines. The biomass decrease caused by cotyledon removal can be partially rescued by exogenous sucrose or auxin with different genotypes responding to sucrose and/or auxin differently. Cotyledon removal has different effects on heterosis in different hybrids. After cotyledon removal, in C24xLer hybrids, both growth and heterosis were reduced in similar proportions, but the level of hybrid vigor was reduced as a proportion of growth in C24xColumbia (Col) and ColxLer hybrids. The removal of cotyledons at 4 DAS markedly decreased the level of growth and eliminated the heterotic phenotype of Wassilewskija (Ws)/Ler hybrids. In mutant Ws/Ler hybrids which had a reduced level of photosynthesis in the cotyledons, there was a reduction in plant growth and loss of heterosis. The variation in contribution of cotyledons to heterosis in different hybrids indicates there are multiple pathways to achieve heterotic phenotypes.
KeywordsAuxin Heterosis Photosynthesis PHYTOCHROME-INTERACTING FACTOR 4 (PIF4) Shi-yo-u 1 (cyo1) Snowy cotyledon 2 (sco2)
Day after sowing
INDOLE-3-ACETIC ACID INDUCIBLE 29
LIGHT-HARVESTING CHLOROPHYLL B-BINDING 2
PHYTOCHROME-INTERACTING FACTOR 4
PHOTOSYSTEM I SUBUNIT O
Snowy cotyledon 1
We thank Dr. Ken-ichiro Takamiya in Tokyo Institute of Technology and Professor Barry Pogson at the Australia National University for providing cyo1 and sco2 mutant seeds, Aihua Wang and Bjorg Sherman for technical assistance, Neil Smith, Dr. Ian Greaves and Dr. Anyu Zhu for helpful discussion and suggestions on this project, Dr. Ming-Bo Wang, Dr. Masumi Robertson and Dr. TJ Higgins for manuscript reviewing.
Compliance with ethical standards
Conflict of interest
The authors declare no competing interests.
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