Plant & zo
The science of plants and more
Light on: Go
Water is an essential part of photosynthesis, the reaction that makes energy for plants. To get the water to the reaction, veins are essential. These pipelines transport the water form the roots to the light. As the water needs to get to the light, light influences the placement of these veins. Consequently, in a just germinated, still underground seedling doesn’t have fully formed veins. Only when it sticks its head above the ground will the veins develop. Long was unclear how light is giving the go ahead for this.
Preparations for future veins are made when seedlings are still in the dark. But those vein precursors have to wait to go ahead. In the dark the TDIF-PXY/TDR complex stops them. When the seedling reaches the light, the TDIF-PXY/TDR complex disappear like snow in spring. Researchers for the United Kingdom found out how light chases away the TDIF-PXY/TDR complex.
Light turns off the PIF gen-on switch, so turning off the TDIF-gene as well
For this the researchers analysed which genes respond to light. It turned out that light turns off the gene for PXY as well as TDIF. The question still remained how light turns those genes off, which gene-on/off switch did it use. To get the answer the researchers used a gene-on switch predictor program to predict the gene-on switch for the light responding genes. In the list of predictions, the researchers found light reacting gene-on switchers, the PIFs. Checking if the PIFs are indeed the looked-for gene-on switches, the researchers analysed plants without any PIFs. There they found little PDIF. The PIFs are thus needed to turn-on the PDIF gene.
To let the TDIF-PXY/TDR complex disappear, light turns off the PIF gen-on switch. So turning off the TDIF-gene as well. And without TDIF no TDIF-PXY/TDR complex. Now the vein precursors can get going, laying the pipeline for the water to get to the light.
Shraboni Ghosh, Joseph F. Nelson, Geoffrey M.C. Cobb, J. Peter Etchells, and Miguel de Lucas (2022) Light regulates xylem cell differentiation via PIF in Arabidopsis Cell Reports 40, 111075 https://doi.org/10.1016/j.celrep.2022.111075