Maternal light environment interacts with genotype in regulating seed photodormancy in tobacco

The environment experienced by tobacco seeds during maturation affects subsequent germination. However, its molecular mechanism is poorly understood. This study aimed to reveal the effects of maternal light environment, genotypes, and their interactions on seed photodormancy in tobacco. The results showed that freshly harvested seeds (FS) of majority varieties (strong-photodormant type, dark-germination of FS is less than 50%) in tobacco could not germinate in the dark, while seeds of minority varieties (shallow-photodormant type, dark-germination of FS is more than 50%) that matured in some environments could germinate independent of light and did not require the duration of after-ripening. The transcriptome comparisons of strong- and shallow-photodormant seeds revealed that the expression of genes involved in light-activated plant hormone signals for strong-photodormant seeds showed opposite changes when the seeds were incubated under light and in the dark. NtPHYB1K326, a homologous gene of Arabidopsis thaliana (Arabidopsis) phytochrome B (PHYB) that in the light-activated plant hormone signals pathway during seed germination, was investigated in this study. The germination frequency of NtPHYB1K326 overexpressing (NtPHYB1K326-OE) seeds was higher than that of wild type (WT) and NtPHYB1K326 RNA interference (NtPHYB1K326-RNAi) seeds in the dark. Interestingly, seed germination in the dark was strongly influenced by the light environment. The seeds showed more germination in the dark when mother plants matured under shading environments than under natural environments. Different types of photodormant seeds or NtPHYB1K326-transgenic seeds showed similar results. These findings illustrated that seed photodormancy could be a heritable trait but was strongly influenced by the light environment of maternal plant development.