MBD1, MBD2, MBD3 and MBD4 proteins participate in abiotic stress responses

MARISOL GIUSTOZZI; JULIA I. QÜESTA; PAULA CASATI

Congreso; Congreso SAIB 2022; 2022

Plants are sessile organisms so they are exposed to different unfavorable environmental conditions, suchas high levels of ultraviolet B radiation, salinity and drought conditions. These environmental conditionscause different damages to macromolecules such as proteins, RNA and DNA. In particular, DNA damagemust be repaired for survival.In eukaryotes, DNA is organized in a complex and dynamic structure, which is chromatin. The nucleosomeis the basic unit of chromatin and is composed of a histone octamer wrapped by 147 base pairs of DNA.The chromatin structure is flexible to allow the processes of transcription, replication, recombination andDNA repair to take place. Therefore, histones are subject to multiple posttranslational modifications, whichinclude acetylation, methylation, ubiquitination and phosphorylation. One of these regulations that alterschromatin affinity is DNA methylation; in plants and animals, the cytosines are modified by the additionof a methyl group. DNA methylation is usually associated with a repressed chromatin state. There arespecialized methyl cytosine binding domain (MBD) proteins that have the ability to interpret thesemodifications. MBD proteins act in concert with chromatin remodeling complexes, histone deacetylaseproteins and histone methyltransferases to establish repressive chromatin and play a biological role ingenomic stability. Previous studies from our laboratory showed that maize plants deficient in theexpression of one MBD protein, MBD101, presented a laxer chromatin, showing a higher sensitivity to UV-Bradiation with increased DNA damage after a treatment. In Arabidopsis there are 5 proteins homologousto MBD101: MBD1, MBD2, MBD3, MBD4 and MBD12. Apart from the conserved MBD domain, these proteinsalso carry a CW-type Zinc Finger (CW-Zf), and thus we refer to this subfamily as CW-MBDs. Therefore, theaim of our work was to study the role of MBD1, MBD2, MBD3, MBD4 proteins in the response to UV-B radiationand high salinity concentrations. We observed that mbd1 , mbd2 , mbd3 and mbd4 mutants and mbd1mbd2 mbd4 and mbd2 mbd3 mbd4 triple mutants showed more DNA damage compared to WT Col-0plants after exposure to UV-B radiation. However, plants deficient in MBD proteins showed a lower numberof dead cells after exposure to UV-B radiation. In addition, a similar response was observed when mbd1 ,mbd2 , mbd3 and mbd4 mutants and mbd1 mbd2 mbd4 and mbd2 mbd3 mbd4 triple mutants wereexposed to salt stress. Hence, the mutants mbd1, mbd2, mbd3, mbd4 and the triple mutants mbd1 mbd2mbd4 and mbd2 mbd3 mbd4 showed increased resistance to UV-B radiation and salt stress conditions.Thus, MBD proteins under study act in response to UV-B and salt stress.