Secret code
Sometimes old findings appear to be not completely correct. That was what a team of international researchers led by Christian Hardtke found out when they studied the brassinosteriods receptors more closely.
Brassinosteroids are one of the plant hormones that have a hand in about everything that has to do with growth and development. When plants are missing one of the receptors that detect brassinosteriods, then they develop less well. They stay, for example, small. One of its receptors, BRI1, is located mainly in the roots. But when 18 years ago the researchers first analysed its function, it appeared that in absence of BRI1 the BRI1 gen only needed to be turned on in one cell type to rescue root development. Something that is quiet strange when you think about it.
Therefore the researchers decided to find out why this was the case. First they repeated the initial experiments. Of which the results showed that indeed when the BRI1 gen with a fluorescent tag is turned on only in the cortex, then it appeared to compensate the absence of BRI1 in all root cells.
The DNA code of the BRI1 gene contains extra information about where the gene needs to be turned on
But then the researchers studied the expression of the BRI1 gen with a really weak gene activator. The fluorescent tag was hardly visible. Not only in the expected cell types, but the whole root had a weakly fluorescent glow.
Subsequently the researchers did something unexpected. They recoded the BRI1 gene, so that it makes the same protein with a different DNA sequence. The researchers gave this recoded BRI1 gene a specific gene on-switch. Only this time there appeared to be no weak fluorescent glow in the rest of the root. The root growth of BRI1 missing plants also did not recover when the her-coded BRI1 gene was only turned on in cortex cells.
The DNA code of the BRI1 gene contains apparently extra information about where the gene needs to be turned on. With only this information the gene is barely active, just enough to keep the development of the whole plant going. Is that information missing, then the gene stays off, unless it gets a strong on-switch.
Literature
Noel Blanco-Touriñán et al., The brassinosteroid receptor gene BRI1 safeguards cell-autonomous brassinosteroid signaling across tissues. SciAdv. 10, eadq3352(2024). DOI:10.1126/sciadv.adq3352
Plant en Zo 