TY - JOUR
AU - Whitelam, Garry C.
AB - The photocontrol of hypocotyl elongation has been studied in two transgenic lines of Arabidopsis thaliana which contain elevated levels of phytochrome B encoded by either an introduced rice‐ or Arabidopsis‐derived cDNA driven by the 35S CaMV promoter. Inhibition of hypocotyl growth in etiolated seedlings of the phyB‐transformed lines was saturated at photon fluence rates of continuous red light (R) which were markedly lower than those required for inhibition of growth in seedlings of the isogenic wild‐type (WT). Inhibition of hypocotyl growth in etiolated seedlings of the phyB‐transgenic lines under continuous far‐red irradiation (FR), however, showed the same relationship with fluence rate as WT. Light‐grown seedlings of the phyB‐transgenic lines responded to end‐of‐day FR by an acceleration of growth, in a manner comparable with WT. This response was unaltered when the end‐of‐day FR was extended from a 15 min pulse to 14 h of continuous irradiation. The response of light‐grown, phyB‐transformed seedlings to decreasing R:FR ratio was also qualitatively similar to WT, i.e. increased elongation growth of the hypocotyl and petioles occurred under low R:FR quantum ratio. However, absolute elongation growth was markedly less in the transgenic seedlings at all R:FR ratios tested than in WT. Together, these data indicate that seedlings over‐expressing phytochrome B are more responsive to R than are WT, but are unaltered in their responsiveness to FR. By contrast, seedlings overexpressing phytochrome A are more responsive than WT to both R and FR; whereas the phytochrome B‐deficient mutant hy3 is unresponsive to R while retaining WT‐like responsiveness to FR. These data indicate that in WT etiolated seedlings phytochrome A mediates the effects of continuous FR, and phytochrome B the effects of continuous R. The evidence thus supports the conclusion that these two molecular species of the photoreceptor have differential regulatory roles in the plant.
TI - Photoresponses of transgenic Arabidopsis seedlings expressing introduced phytochrome B‐encoding cDNAs: evidence that phytochrome A and phytochrome B have distinct photoregulatory functions
JF - The Plant Journal
DO - 10.1046/j.1365-313X.1993.04010019.x
DA - 1993-07-01
UR - https://www.deepdyve.com/lp/wiley/photoresponses-of-transgenic-arabidopsis-seedlings-expressing-5jhTcRIwoe
SP - 19
EP - 27
VL - 4
IS - 1
DP - DeepDyve
ER -