Response of hrpZPsph-transgenic N. benthamiana plants under cadmium stress.

The hrpZPsph gene from Pseudomonas syringae pv. phaseolicola, in its secretable form (SP/hrpZPsph), has previously proven capable of conferring resistance against rhizomania disease as well as abiotic stresses in Nicotiana benthamiana plants, while enhancing plant growth. This study aimed at investigating the response of SP/hrpZPsph-expressing plants under cadmium stress. Transgenic N. benthamiana lines, homozygous for the SP/hrpZPsph gene, and wild-type plants were exposed to Cd at different stress levels (0, 50, 100, 150 µΜ CdCl2). Plants' response to stress was assessed at germination and at the whole plant level on the basis of physiological and growth parameters, including seed germination percentage, shoot and root length, total chlorophyll content, fresh and dry root weight, as well as overall symptomatology, and Cd content in leaves and roots. At germination phase, significant differences were noted in germination rates and post-germination growth among stress levels, with Cd effects being in most cases analogous to the level applied but also among plant categories. Although seedling growth was adversely affected in all plant categories, especially at high stress level, lines #6 and #9 showed the lowest decrease in root and shoot length over control. The superiority of these lines was further manifested at the whole plant level by the absence of stress-attributed symptoms and the low or zero reduction in chlorophyll content. Interestingly, a differential tissue-specific Cd accumulation pattern was observed in wt- and hrpZPsph-plants, with the former showing an increased Cd content in leaves and the latter retaining Cd in the roots. These data are discussed in the context of possible mechanisms underlying the hrpZPsph-based Cd stress resistance.

Effect of two exogenous plant growth regulators on the color and quality parameters of seedless table grape berries.

Some red-pink table grape varieties, cultivated in warm climates, can fail in achieving the right level of anthocyanins responsible for the intense and uniform red color of berries. Nowadays, this is becoming an important technological issue in the Mediterranean area, which may result in decreasing market acceptance and potential economic value of table grape. Usually, plant growth regulators or phytohormones, such as S-ABA, can overcome this problem because they drive the accumulation of anthocyanins over the ripening season. Harpin proteins (HrP), which enhance the plant disease resistance, may be supposed to stimulate the anthocyanins biosynthesis in grape skin if applied close to veraison. Therefore, this research aimed at comparing the effect of HrP and S-ABA over the anthocyanin and color improvement of Crimson Seedless table grape grown in Southern Italy. For the first time, the exogenous treatment with HrP showed as effective as the less sustainable S-ABA one in favoring the anthocyanin accumulation, leading to peonidin-3-O-glucoside, cyanidin-3-O-glucoside, and malvidin-3-O-glucoside values up to 4 folds higher than control grapes and giving rise to a greater concentration of the more stable acylated anthocyanins. Overall, the color of berries was improved but keeping high the other quality characteristics.