Double break
One of a seedlings first reactions to salt is stepping on the break. Now researchers from Scotland and Italia show in the New Phytologist how the protein HDC1 is regulating how hard the plant is pressing this break.
To make sure that stress genes are not accidentally turned on they are decorated by markings that make them unreadable. Then, when stress does occur, HDAC protein complexes remove those markings. A by the researchers earlier discovered part of this complex is HDC1. But how HDC1 is making those stress genes readable again was still unknown. That the researchers aimed to change.
Their first priority was to find out which genes HDC1 regulates. Sequencing the RNA, showed the researchers that already 3 hours after exposure to salt a lot of genes were turned on or off. In addition the researchers studied with help of ChIP-Seq to which genes HDC1 binds in response to salt stress. This resulted in four genes ABI3, LEA, MAF5, and RAB18. When ABI3 and LEA are turned on they repress germination and growth of seedlings.
HDC1 to regulates precisely the amount of ‘panic’ that is needed
Subsequently the researchers studied which markings HDC1 changes by salt stress. For this they used plants with and without HDC1. In non-stressed plants the researchers did not see any difference in the markings of plants with or without HDC1. But by the occurrence of salt stress, then in plants without HDC1 the genes ABI3, LEA, MAF5, and RAB18 had more acetyl-markings, but less methyl markings. Together this shift in marking turned on ABI3, LEA, MAF5 and RAB18, causing growth to stop.
Interaction with histone H1 was needed for changing the methyl markings. In the absence of histone H1 the genes ABI3, LEA, MAF5, and RAB18 were less marked with methyl-markings during salt stress. But only those markings were affected, not the acetyl markings. As only the methyl-markings change, ABI3, LEA, MAF5, and RAB18 are turned on only a little bit, slowing growth, but not stopping it.
As HDC1 is adjusting both the methyl as acetyl markings, it has the function of a double break. Enabling HDC1 to precisely regulate the amount of ‘panic’ that is needed. Preventing the plant to enter into a situation where it can not get out of. Like in the case of salt stress by germination, as the possibility exist that with a little more growth the root will encounter a patch without too much salt.
Literature
Perrella, G., Fasano, C., Donald, N.A., Daddiego, L., Fang, W., Martignago, D., Carr, C., Conti, L., Herzyk, P. and Amtmann, A. (2023), Histone Deacetylase Complex 1 and histone 1 epigenetically moderate stress responsiveness of Arabidopsis thaliana seedlings. New Phytol. https://doi.org/10.1111/nph.19165
Plant en Zo 