Phytochrome A affects stem growth, anthocyanin synthesis, sucrose-phosphate-synthase activity and neighbour detection in sunlight-grown potato

YANOVSKY, MJ; ALCONADA MAGLIANO, T; MAZZELLA, MA; GATZ, C; THOMAS, B; CASAL, JJ

PLANTA

SPRINGER

Año: 1998 vol. 205 p. 235 - 241

0032-0935

Phytochrome action in fully de-etiolated sun- light-grown potato (Solanum tuberosum L.) was studied by comparing wild-type (WT) plants and transgenic plants with either a sense or an anti-sense phytochrome A (phyA) construction. Radial stem growth, antho- cyanin levels, and sucrose-phosphate-synthase activity were directly related to the levels of phyA (severely reduced in transgenics with anti-sense phyA, normal in WT and increased in transgenic with sense phyA). In contrast, longitudinal stem growth was inversely related to the levels of phyA. Phytochrome A in¯uenced stem- extension growth responses to red/far-red ratios per- ceived by stable phytochrome[s]. First, far-red light re¯ected by non-shading neighbours promoted stem growth in WT plants but transgenic plants with either increased or reduced phyA levels failed to respond to this light signal. Second, plants with low phyA levels also showed impaired sensitivity to reductions in end-of- day red/far-red ratios. In addition, phyA appears to perceive changes in irradiance reaching the stem: lower- ing the amount of red plus far-red light reaching the stem promoted stem growth in WT plants. This e?ect was exaggerated in phyA overexpressors and absent in phyA underexpressors. Thus, phyA is active in fully de- etiolated, sunlight-grown plants.Solanum tuberosum L.) was studied by comparing wild-type (WT) plants and transgenic plants with either a sense or an anti-sense phytochrome A (phyA) construction. Radial stem growth, antho- cyanin levels, and sucrose-phosphate-synthase activity were directly related to the levels of phyA (severely reduced in transgenics with anti-sense phyA, normal in WT and increased in transgenic with sense phyA). In contrast, longitudinal stem growth was inversely related to the levels of phyA. Phytochrome A in¯uenced stem- extension growth responses to red/far-red ratios per- ceived by stable phytochrome[s]. First, far-red light re¯ected by non-shading neighbours promoted stem growth in WT plants but transgenic plants with either increased or reduced phyA levels failed to respond to this light signal. Second, plants with low phyA levels also showed impaired sensitivity to reductions in end-of- day red/far-red ratios. In addition, phyA appears to perceive changes in irradiance reaching the stem: lower- ing the amount of red plus far-red light reaching the stem promoted stem growth in WT plants. This e?ect was exaggerated in phyA overexpressors and absent in phyA underexpressors. Thus, phyA is active in fully de- etiolated, sunlight-grown plants.