ARS | Publication request: EXPRESSION OF CHLOROPLAST PROTEIN SYNTHESIS ELONGATION FACTOR, EF-TU, IN TWO LINES OF MAIZE WITH CONTRASTING TOLERANCE TO HEAT STRESS

Submitted to: Journal of Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 6, 2006
Publication Date: January 6, 2006
Citation: Momcilovic, I., Ristic, Z. 2006. Expression of chloroplast protein synthesis elongation factor, ef-tu, in two lines of maize with contrasting tolerance to heat stress. Journal of Plant Physiology 1674:90-99.

Interpretive Summary: When plants are stressed by heat in their environment, one proposed response is that they produce proteins that make them more tolerant to such heat stress. In maize (corn), a protein called EF-Tu that is produced by the chloroplast structures, has been implicated as such a heat tolerance protein. We investigated the levels of EF-Tu produced by heat tolerant and heat resistant lines of maize at different stages of plant growth. Heat tolerant maize lines produced EF-Tu protein in plants if all ages (except 5-day-old shoots) and showed additional accumulation of EF-Tu under conditions of heat stress. In contrast, in the heat sensitive maize lines, EF-Tu protein was accumulated only in plants up to 14 days old. Heat resistant plants contained higher levels of EF-Tu than heat sensitive plants supporting the proposed involvement of this protein in heat stress tolerance. Breeders may be able to use this information to develop plant lines that can withstand higher heat stress conditions in our environment by selecting for genes that produce EF-Tu.

Technical Abstract: Maize chloroplast protein synthesis elongation factor, EF-Tu, has been implicated in heat tolerance, and previous studies have shown that under heat stress this protein accumulates in 14-d-, 17-d-, and 21-d-old plants of maize genotypes with increased tolerance to stress. In the present study, we investigated the expression of EF-Tu genes in heat tolerant, ZPBL 1304, and heat sensitive, ZPL 389, maize lines during early stages of their development (5 – 21-d-old plants) under both control and heat stress conditions. We also investigated the expression of EF-Tu in mature plants of these lines under field conditions and assessed heat tolerance in young seedlings at different stages of their development. The expression of EF-Tu was studied by determining the relative levels of EF-Tu protein and the steady state levels of EF-Tu mRNA. Chloroplast EF-Tu showed differential expression during early stages of plant development, and the heat tolerant and the heat sensitive line differed in the expression of EF-Tu under heat stress. In ZPBL 1304, plants of all ages (except 5-d-old shoots) showed heat-induced accumulation of both EF-Tu transcript and EF-Tu protein. In contrast, in ZPL 389, only plants up to 14 d of age displayed increased accumulation of EF-Tu under heat stress. The increase in the relative level of EF-Tu in ZPL 389 was not preceded by an increase in the steady state level of EF-Tu mRNA. Under heat stress, the relative levels of EF-Tu correlated positively with plant heat tolerance. The results are consistent with the hypothesis that maize EF-Tu plays a role in heat tolerance and suggest that under heat stress conditions, the regulation of expression of EF-Tu may be different in the heat tolerant and heat sensitive maize lines.