In addition, LUH also interacts with SLK1 and SLK2 and functions redun dantly with LUG in abaxial organ identity. Until re cently, LUH function in addition to its minor role in development was not known. Several recent reports any other enquiries in dicate that LUH plays an important Inhibitors,Modulators,Libraries role in regulating pectin structure and mutants Inhibitors,Modulators,Libraries lacking LUH fail to release mucilage from the seed coat. One relevant target of LUH is MUM2, a B galactosidase involved Inhibitors,Modulators,Libraries in the modifi cation of the mucilage. At present, there are two plausible mechanisms to account for MUM2 regulation. The first is by LUH acting as a direct positive regulator of MUM2. The other mechanism involves LUH acting as negative regulator of a MUM2 repressor. Although LUH shows significant sequence similarity with LUG, the molecular function of LUH remains un clear.
The only known function of LUH is its major role in mucilage secretion in Arabidopsis. In this study, we present results indicating involvement of LUH in the abi otic stress response. We demonstrate that LUH functions as a transcriptional repressor similar to Gro/Tup1 family proteins. Additionally, Inhibitors,Modulators,Libraries we show that the conserved LUFS domain in LUH physically interacts with adaptor proteins SLK1 and SLK2 which do not show repressor activity themselves. The luh, slk1 and slk2 mutant plants shows el evated salt and osmotic stress tolerance and higher ex pression levels of abiotic stress responsive gene under non stress conditions. In addition, LUH physically inter acts with histone H2B and H3 and either directly or indir ectly regulates chromatin structure at the abiotic stress responsive genes.
These data provide an insight into the novel roles for LUH, SLK1 and SLK2 in abiotic stress re sponse gene regulation and illuminate LUH function in chromatin remodeling. Results luh 4, slk1 1 and slk2 1 plants exhibit tolerance to salt and osmotic stress Comparison Inhibitors,Modulators,Libraries of expression profiles between LUG and LUH revealed that both the genes are expressed at com parable levels in all tissues under normal condition. Interestingly, LUH expression level is elevated in both biotic and abiotic stress in contrast to LUG which remained unchanged or reduced. Since LUH ex pression is enhanced in abiotic stress and interacts with SEU, we sought to determine whether the LUH SEU complex plays a role in abiotic stress. We subjected luh 4 and seu 1 plants to salt and osmotic stress.
Plants with mutation in SEU showed unchanged tolerance to salt and osmotic stress that could be attributed to the functional redundancy within the SEU family proteins. Arabidopsis encodes three SEU like proteins and these proteins function redundantly with SEU in flower devel opment. We available hypothesized that SLK may be in volved in the abiotic stress and functions redundantly with SEU in flower development, because slk1 1 and slk2 1 single and double mutants do not show any defect in flower development.