First assessment of the expression and biochemical analysis of the whole thioredoxin maize family

DRINCOVICH MF; FIGUEROA CM; TONETTI T; ALVAREZ C

Rosario

Congreso; LIX Reunión Anual de la SAIB; 2023

SAIB

Thioredoxins (Trxs) are small ubiquitous proteins containingan extremely reactive site with a highly conserved sequence, participating invarious reactions requiring the reduction of disulfide bonds in selected targetproteins. Trxs are encoded by a multigene family and are usually classifiedaccording to their function, structure and subcellular localization. Plantspossess the largest Trx family across kingdoms; however, little is known abouttheir function in plants when compared with other organisms. In this work weclassified all the ten putative Trxs from maize, which is the largest family ofTrxs known so far, using the Trx family from Arabidopsis thaliana as template.In maize, Trxs cluster into seven groups related to their presumed evolutionaryorigin. We then measured the relative abundance of all the putative Trxtranscripts in the base, middle, and top leaf sections and found that, ingeneral, accumulation was higher in the middle section. As maize leaves havetwo specialized cells, we further analyzed Trx transcripts in fractionsenriched in bundle-sheath cells (BSC) and mesophyll cells (MC). Our resultsshowed that certain Trx transcripts are preferentially accumulated in BSC(ZmTrx-BSC) or MC (ZmTrx-MC). In silico analysis of the promoters of the genesencoding ZmTRX-MC and ZmTRX-BSC indicate that they would be responsive toethylene and light, respectively, which is consistent with the putativeinvolvement of ZmTrx-BSC in the photosynthetic process. Based on these results,we focused our attention on the biochemical and kinetic properties of theseTrxs. To better understand their function in vivo, we designed, obtained andexpressed site-directed mutants in the resolutive cysteine of each Trx isoform,ZmTrx-BSC-MutCys2 and ZmTrx-MC-MutCys2, and performed different bindingprotocols to find their specific protein targets. These results are the startingpoint to uncover the pathways in which maize Trxs isoforms are involved.