Proceedings of the XLVII Italian Society of Agricultural Genetics - SIGA Annual Congress

Verona, Italy - 24/27 September, 2003

ISBN 88-900622-4-X

Oral Communication Abstract - S4d

OVEREXPRESSING PHYA GENE CHANGES THE CHERRY PLANT SENSIBILITY TO THE LIGHT SIGNAL

R. MULEO*, C. IACONA**, M.C. INTRIERI*, F. NICESE***, S. MANCUSO***, R. GUERRIERO**, F. LORETI**, B. THOMAS****

*) DiProV, Università della Tuscia (VT), Italy

**) DCDSL, Università di Pisa, Italy

***) Dipartimento di Ortoflorofrutticoltura, Università di Firenze

****) DPGB, HRI, Wellesbourne, Warwick, CV35 9EF, UK

cherry, development, Phytochrome A, Shade Avoidance Response, transgenic plants

Light also acts as a signal of environmental conditions surrounding the plants. There are photoreceptors that function as signal transducers to provide information that controls physiological and morphological responses. Through these pigments, plants have the ability to perceive subtle changes in light composition for initiation of physiological and morphological changes. Known photomorphogenic receptors include phytochrome, cryptochrome and phototropin. Aim of this work was to unravel the effect of phytochrome A overexpression in cherry plants grew under canopy competition, following their reaction to the syndrome of shade avoidance response.

The cherry genotype Colt (P.avium x P.cerasus) was infected with a binary vector systems of Agrobacterium tumefaciens carryng NptII and rice phyA genes, under 35S promoter. From molecular analyses 9 clones resulted positive to the trasformation, and both genes were successfully inserted. All clones expressed the transgenes. The photobiological reactivity of all clones was evaluated in an in vitro screening system. Result showed that the pattern of plantlets development of only four clones was differently regulated by red and far-red light qualities respect to wt.

On the basis of these results, we evaluated the role of the overexpressed phyA gene on to the perception of light qualities in vivo adapted plants: under simulated interaction between plants and light of the 4 clone and wt; while only two clones and wt were studied in real interaction between plants. (Pn), transpiration rate (E) and water use efficiency (WUE) was measured on three fully expanded leaves on every plant of the two different stands under conditions of light saturation (PAR > 1000 µmol m^-2s^-1).

Plant grew in simulated conditions was surrounding by a light filter, that enriched in red or far-red incoming light direct horizontally on to sapling stem. Mixed stands (that are formed by one clone and wt in chessboard grid) were adopted to grow plants in simulated community canopy, for two years. In both conditions a strong proximity signals were generated. Phenotypic aspects of plant development (stem height, growth, leaf area, branch formation, stomata dimension and formation, chlorophyll content and finally photosynthetic activity) were changed and an intrinsic growth rate was recognised between wt and transformed plants. Net photosynthesis was significantly lower in the transformed PA plants than the wt plants, as the PO plants turned out to be more efficient than the wt ones. The transpiration rate was significantly higher in PO clones compared to wt plants, while water use efficiency (Pn/E) did not differ in all genotypes. Considering the same data after having grouped them in external, middle and internal data according with the position of the plants in the stands, PO plants seemed to be more sensitive to light intensity, as a matter of fact the internal plants showed a higher efficiency in term both of Pn and WUE. A clear relation between the growth and development of transgenic plants and the established concentration of Pfr and the light intensity were also evident, with colt wt and clones plants reacting to neighbours in a divergent dynamic ways. As resulting of these changes, the sensivity to shade and HIR conditions varied among the four clones, ranged from strong shade-tolerant to week shade-tolerant.

This research has been partially supported by: MURST project “Vegetative habit modification of fruit trees through genetic transformation and eco-physiological evaluation of the trangenes”; CNR-Agenzia2000.