Detection of crowding in shoots induces root elongation in the soil

GONZALEZ, CARINA VERONICA; BOCCALANDRO, HERNÁN ESTEBAN

Ciudad de Mendoza

Congreso; XXVI Reunión Científica Anual Sociedad de Biología de Cuyo; 2008

Sociedad de Biología de Cuyo de Mendoza

Phytochrome B (phyB) is a photoreceptor that plays a key role modulating plant growth and development. As incident solar light penetrates a plant canopy, it suffers a gradual attenuation in light quantity and in the red (R) to far-red light (FR) ratio (R/FR). This signal is detected by the phyB, which triggers a ‘shade-avoidance syndrome’ that involves petiole and stem elongation, increasing the chance of shoots to forage for light.The purpose of this work was to assess whether phytochrome B can regulate root morphology in soil when detecting neighbour associated signals (R/FR) in shoots, using genetic and physiological approaches. Wild type plants (WT), phyB null mutants (that constitutively evoke the shade avoidance syndrome) and PHYB overexpressors (blind to detect neighbours) were grown under white light in sand-filled pots placed in a growth chamber. WT plants were also exposed to a low R/FR ratio, simulating neighbours. We found that plants grown under lower R/FR presented longer roots. In agreement, phyB mutation increased root length (cm) (phyB-5: 4.8±0.3 vs. WT: 2.9±0.2; phyB-9: 3.6 ±0.2 vs. WT: 3.0±0.2) while PHYB overexpression decreased it (35S:PHYB: 1.7±0.2 vs. WT 3.8±0.3; 35S:PHYB-GFP 2.0±0.2 vs. WT: 3.0±0.2). In summary, phyB promotes root elongation in soil, after perceiving light signals associated to potential competitors above ground. This mechanism would improve the chances of plants to acquire water and nutrients in crowded plant stands.