Phenotypic changes in Solanum lycopersicum due to expression of NADP-malic enzyme in phloem companion cells

SAPER, CAROLINA; GUINDON, MARÍA FERNANDA; DRINCOVICH, MA. FABIANA; OITAVEN, PABLO; MÜLLER, GABRIELA L.

Congreso; Reunión anual Edición LVIII; 2022

Plants are frequently subjected to numerous adverse environmental conditions that can affect the normal growth and development of plants. Evidence indicates that NADP-malic enzyme (NADP-ME), key enzyme regulating malic acid metabolism, is induced by diverse biotic and abiotic stresses. It has been shown that it is involved in various processes, including housekeeping roles such as the maintenance of cellular pH, generation of reductive power, regulation of guard cells,regulation of osmotic pressure for stomatal movement and fruit ripening. The plastidic non-photosynthetic NADP-ME from Zea mays has been integrated into the Solanum lycopersicum genome under the control of SUC2 promoter from Arabidopsis, which drives the expression to the phloem companion cells of all green tissues. In this work, two tomato transgenic homozygous lines (SUC174 and SUC176) obtained from one transformation event were characterized phenotypically and compared with WT plants. The expression of NADP-ME in the root, stem, leaves and flowers was verified by quantitative real-time PCR in transgenic plants while it was undetectable in WT plants. Five plants of each line were evaluated in relation to flowering time, plant height, internode length, number and length of leaves, number of leaflets in leaf, length and width of terminal leaflet, weight and diameter of fruit, number of seeds per fruit and weight of seeds. Mean values were compared through Student’s t test at a significance level of p < 0.05. The analyses indicated that WT plants had opened the first flower before SUC lines (47.80 ± 1.16 vs 56.87 ± 1.27 days). At this stage transgenic plants were larger (13.35±0.29 vs 10.56±0.85 cm), with longer internode lengths (1.523±0.085 vs 1.130±0.091 cm) and more average leaflets by leaf (4.27±0.09 vs 3.83±0.10). The first ten mature fruits of every plant were harvested and analyzed. Transgenic tomatoes showed superior values for weight (3.61±0.13 g) and diameter (19.71±0.28) than WT tomatoes (2.81 ± 0.18 g and 18.16 ± 0.47 cm, respectively) but the weight of the transgenic seeds decreased slightly (2.27±0.07 vs 2.99±0.21 mg). These preliminary results indicated detectable changes under stress-free conditions in tomato lines that express NADP-ME in phloem companion cells, being the first step to advance in the study of changes that occur in this fundamental tissue responsible of photosynthates transport, shedding light on new strategies to deal with global climate change and the growing demand for food.