The role of the transcription factor AtHB22 during the early stage of Arabidopsis germination and development

TRIONFINI, V.; CANAL, M.V.; CHAN, R.L.; ATTALLAH, C.; WELCHEN, E.

Santa Fe

Congreso; XXXIII Argentinian Meeting of Plant Physiology (RAFV); 2021

RAFV

AtHB22 is an Arabidopsis Transcription Factor (TF) belonging to the HD-Zip I (Homeodomain-leucine zipper I) family. These TFs are involved in the control of plant development and orchestrating responses to environmental factors. To gain more insight into the role of AtHB22, we studied phenotypic characteristics of Arabidopsis plants with altered expression of this TF at different stages of development. The athb22 mutant plants exhibit a delay in germination both under control conditions and in presence of Abscisic acid (ABA) in the growth media, showing increased sensitivity to ABA at this stage related to wild-type (WT) plants. To analyze the expressionpattern of AtHB22, we generated Arabidopsis plants expressing the GUS reporter gene under the control of its putative promoter. We observed GUS expression in embryos at early stages, increasing during the imbibition process and diminishing during the addition of exogenous ABA. In agreement, AtHB22 transcript levels are higher in imbibed seeds than in dry seeds and are regulated by ABA in WT plants. AtHB22 expression is increased in the background of abi4 mutants, while the opposite behavior is observed during germination in ABI4 overexpressor plants. On the other hand, GUS expression is detected in the shoot apical meristem (SAM) and the leaf margin till 12 days after sawing. The AtHB22 expression pattern and the phenotype of overexpressor plants are similar to that of its paralog AtHB51. Expression of AtHB51 is deregulated in the background of plants with altered expression of AtHB22. Our results suggest a putative role of AtHB22 during germination and at the early stages of leaf development in Arabidopsis. More experiments are necessary to elucidate the role of AtHB22 and the pathway of plant hormones that regulate these events.