Plants frequently encounter relatively low and fluctuating potassium (K⁺) concentrations in soil, with roots serving as primary responders to this stress. Histone modifications, such as de-/acetylation, can function as epigenetic markers of stress-inducible genes. However, the signaling network between histone modifications and low-K⁺ (LK) response pathways remains unclear. This study investigated the regulatory role of Histone Deacetylase Complex 1 (HDC1) in primary root growth of Arabidopsis thaliana under K⁺ deficiency stress. Using a hdc1-2 mutant line, we observed that HDC1 positively regulated root growth under LK conditions. Compared to wild-type (WT) plants, the hdc1-2 mutant exhibited significantly inhibited primary root growth under LK conditions, whereas HDC1-overexpression lines displayed opposite phenotypes. No significant differences were observed under HK conditions. Further analysis revealed that the inhibition of hdc1-2 on root growth was due to reduced apical meristem cell proliferation rather than cell elongation. Notably, the root growth of hdc1-2 showed reduced sensitivity compared to WT after auxin treatment under LK conditions. HDC1 may regulate root growth by affecting auxin polar transport and subsequent auxin signaling, as evidenced by the altered expression of auxin transport genes. Moreover, the organ-specific RT-qPCR analyses unraveled that HDC1 negatively regulates the expression of CBL-CIPK-K⁺ channel-related genes such as CBL1, CBL2, CBL3, AKT1, and TPK1, thereby establishing a molecular link between histone deacetylation, auxin signaling, and CBLs-CIPKs pathway in response to K⁺ deficiency.

Plants frequently encounter relatively low and fluctuating potassium (K+) concentrations in soil, with roots serving as the primary responders to this stress. Histone modifications, such as de-/acetylation, can function as epigenetic marks on stress-inducible genes. However, the signaling network between histone modifications and the low K+ (LK) response pathways remains unclear. This study delves into the regulatory role of Histone Deacetylase Complex 1 (HDC1) in primary root growth of Arabidopsis thaliana under K+ deficiency stress. Using a hdc1-2 mutant line, we observed that HDC1 positively regulates root growth under LK conditions. Compared to wild-type (WT) plants, the hdc1-2 mutant exhibited significantly inhibited primary root growth under LK conditions, whereas HDC1-overexpression lines displayed opposite phenotypes. No significant difference was observed under HK conditions. Further analysis revealed that the inhibition of hdc1-2 on root growth was due to reduced meristem cell proliferation rather than cell elongation. Notably, the root growth of hdc1-2 shows reduced sensitivity compared to WT after auxin treatment under LK conditions. HDC1 may regulate root growth by affecting auxin polar transport and subsequently auxin sensation, as evidenced by altered expression of auxin transport genes. Moreover, our study reveals a brake function of HDC1 in the regulation of CBL-CIPK-K+ channel related genes, thereby establishing a molecular link between histone deacetylation, auxin signaling, and CBL-CIPK pathway in response to K+ deficiency.

The non-specific lipid transfer proteins (nsLTPs) are able to bind various hydrophobic compounds and facilitate the transport of fatty acids between intracellular membranes, and nsLTPs are found in rice endosperm and embryo during seed development. However, whether nsLTPs function as lipid carriers and thereby affect lipid metabolism in rice grains remains unclear. To elucidate whether nsLTPs influence fatty acid distribution in rice, we generated OsLTP10-OE (OsLTP10 overexpression) and OsLTP10-CR (OsLTP10 CRISPR/Cas9) lines. Phenotypic and metabolic analyses indicated that OsLTP10 expression is closely associated with fatty acid (FA) profiles and grain appearance. In general, total fatty acid content in the brown rice of OsLTP10-OE was higher than that in wildtype, but OsLTP10-CR was lower than wildtype. While FA accumulation was altered in both tissues, the endosperm (milled grain) was more severely affected than the bran, with individual FAs in the milled grains of OsLTP10-OE expanding by 31.87–52.00%. Additionally, key grain quality traits were substantially altered; OsLTP10-CR lines displayed a significantly enlarged white-belly chalkiness area alongside a 19.50% reduction in amylose content, whereas OsLTP10-OE lines showed decreased chalkiness and a 7.80% increase in amylose. Overall, the fatty acid content and composition, chalkiness, brown rice size, and amylose were influenced by OsLTP10.