HYPONASTIC LEAVES 1 IS REQUIRED FOR PROPER ESTABLISHMENT OF AUXIN GRADIENT IN APICAL HOOKS OF ARABIDOPSIS

VACS, PAULA; RASIA, RODOLFO; GONZALEZ SCHAIN, NAHUEL

Mendoza

Congreso; LVIII Reunión Anual de SAIB; 2022

Seedlingsgerminating under the soil surface have evolved to an exquisite developmentalprogram termed skotomorphogenesis. In darkness, seedlings rapidly elongate thehypocotyl toward the surface in a desperate search of light, while protectingthe apical meristem against mechanical damage by forming a hook between thehypocotyl and the two closed cotyledons. A proper skotomorphogenic growth mustbe achieved until seedlings reach the light to ensure survival as they dependon limited seed reserves. In our previous work we uncovered that microRNAbiogenesis is necessary for proper skotomorphogenesis in Arabidopsis. Bystudying mutants in the core components of miRNA microprocessor, DICER LIKE 1(DCL1), HYPONASTIC LEAVES 1 (HYL1) and SERRATE (SE), we surprisingly found amicroprocessor-independent function of HYL1 as a repressor of hook development.Our findings have led to hypothesized a possible connection between HYL1 actionin skotomorphogenesis and the well-established and crucial function of thephytohormones auxins in hook development. In this work we dissect differentaspects of auxin biology in HYL1 mutants (auxin sensitivity, transcriptionalresponses, biosynthesis and transport) and found that HYL1 is needed toestablish the auxin gradient in apical hooks. Our research led us to proposethat HYL1 might integrate light/dark and auxin signals to controlskotomorphogenic growth in Arabidopsis.