FIRST ASSESSMENT OF THE EXPRESSION AND BIOCHEMICAL ANALYSIS OF THE WHOLE THIOREDOXIN MAIZE FAMILY

TONETTI, TOMÁS; DRINCOVICH, MARIA F. ; FIGUEROA, CARLOS M.; ÁLVAREZ, CLARISA E.

Rosario

Congreso; LIX SAIB; 2023

SAIB

Thioredoxins (Trxs) are small ubiquitous proteins containing an extremely reactive site with a highly conserved sequence, participating in various reactions requiring the reduction of disulfide bonds in selected target proteins. Trxs are encoded by a multigene family and are usually classified according to their function, structure and subcellular localization. Plants possess the largest Trx family across kingdoms; however, little is known about their function in plants when compared with other organisms. In this work we classified all the ten putative Trxs from maize, which is the largest family of Trxs known so far, using the Trx family from Arabidopsis thaliana as template. In maize, Trxs cluster into seven groups related to their presumed evolutionary origin. We then measured the relative abundance of all the putative Trx transcripts in the base, middle, and top leaf sections and found that, in general, accumulation was higher in the middle section. As maize leaves have two specialized cells, we further analyzed Trx transcripts in fractions enriched in bundle-sheath cells (BSC) and mesophyll cells (MC). Our results showed that certain Trx transcripts are preferentially accumulated in BSC (ZmTrx-BSC) or MC (ZmTrx-MC). In silico analysis of the promoters of the genes encoding ZmTRX-MC and ZmTRX-BSC indicate that they would be responsive to ethylene and light, respectively, which is consistent with the putative involvement of ZmTrx-BSC in the photosynthetic process. Based on these results, we focused our attention on the biochemical and kinetic properties of these Trxs. To better understand their function in vivo, we designed, obtained and expressed site-directed mutants in the resolutive cysteine of each Trx isoform, ZmTrx-BSC-MutCys2 and ZmTrx-MC-MutCys2, and performed different binding protocols to find their specific protein targets. These results are the starting point to uncover the pathways in which maize Trxs isoforms are involved.