ArabidopsisDNA topoisomerase i alpha is required for adaptive response to light and flower development

Abstract

DNA topoisomerase I alpha (TOP1α) plays a specific role in Arabidopsis thaliana development and is required for stem cell regulation in shoot and floral meristems. Recently, a new role independent of meristem functioning has been described for TOP1α, namely flowering time regulation. The same feature had been detected by us earlier for fas5, a mutant allele of TOP1α. In this study we clarify the effects of fas5 on bolting initiation and analyze the molecular basis of its role on flowering time regulation. We show that fas5 mutation leads to a constitutive shade avoidance syndrome, accompanied by leaf hyponasty, petiole elongation, lighter leaf color and early bolting. Other alleles of TOP1α demonstrate the same shade avoidance response. RNA sequencing confirmed the activation of shade avoidance gene pathways in fas5 mutant plants. It also revealed the repression of many genes controlling floral meristem identity and organ morphogenesis. Our research further expands the knowledge of TOP1α function in plant development and reveals that besides stem cell maintenance TOP1α plays an important new role in regulating the adaptive plant response to light stimulus and flower development.

The Tyrosyl-DNA Phosphodiesterase 1β (Tdp1β) Gene Discloses an Early Response to Abiotic Stresses

“…The percentage of cellular mortality and expression of TOP1 isoforms were assessed to gain more insight into cell behaviour during treatments. As DNA topoisomerase I is involved in solving the conformational changes in DNA topology, it plays essential roles in several cellular processes (e.g., replication, transcription, recombination) [ 34 ] as well as in the response to stress agents [ 35 , 36 , 37 ]. It can also act as a damage sensor and cofactor in DNA repair pathways [ 38 , 39 ].…”