The transcription factors AtHB6 and AtHB16 modulate light responses in Arabidopsis development

MIGUEL VIRGINIA N; PEROTTI MARÍA F; CHAN, RAQUEL L.

SANTA FE

Congreso; XXXIII Reunión Argentina de Fisiología Vegetal; 2021

Sociedad Argentina de Fisiología Vegetal

Plants' development is affected by light which is a regulating signal in multiple developmental events. AtHB6 and AtHB16 are transcription factors encoded by paralogous genes belonging to the homeodomain-leucine zipper I family. These proteins were associated with plant development in response to environmental factors, in particular to light illumination conditions. However, functional studies are scarce or directly null for these genes. To elucidate their role, we generated overexpressor and silenced plants, as well as transgenics carrying both promoters driving the expression of the GUS reporter gene. GUS staining was evident in 3-day-old seedlings for both genes, especially in cotyledons in dark conditions in roots . AtHB16 overexpressor seedlings (OX16), grown in complete darkness, exhibited open cotyledons and apical hook with an increased aperture angle. However, they had no chloroplasts and did not develop them even after several days in normal illumination conditions. Moreover, these plants did not present the ethylene triple-response. The cotyledon bleaching was more severe in the presence of AgNO3, an inhibitor of ethylene sensing. Plants overexpressing AtHB6 exhibited a similar phenotype in darkness, but this differential phenotype reverted after placing the plants in the light, whereas AtHB6 silenced plants (amiR6) showed the opposite phenotype. Notably, COP1, PIF1, and EIN3 transcript levels were significantly reduced in OX16 plants, suggesting a loss in the protection to deal with oxidative damage. The repression of these targets could explain the bleaching observed in light by these plants. Altogether, the results indicated that these transcription factors are involved in seedlings' development in response to light illumination conditions.