Background: Although histone deacetylases from model organisms have been previously identified, there is no clear basis for the classification of histone deacetylases under the RPD3/HDA1 superfamily, particularly on plants. Thus, this study aims to reconstruct a phylogenetic tree to determine evolutionary relationships between RPD3/HDA1 histone deacetylases from six different plants representing dicots with Arabidopsis thaliana, Populus trichocarpa, and Pinus taeda, monocots with Oryza sativa and Zea mays, and the lower plants with Physcomitrella patens. Results: Sixty two histone deacetylases of RPD3/HDA1 family from the six plant species were phylogenetically analyzed to determine corresponding orthologues. Three clusters were formed separating Class I, Class II, and Class IV. We have confirmed lower and higher plant orthologues for AtHDA8 and AtHDA14, classifying both genes as Class II histone deacetylases in addition to AtHDA5, AtHDA15, and AtHDA18. Since Class II histone deacetylases in other eukaryotes have been known to undergo nucleocytoplasmic transport, it remains unknown whether such functional regulation also happens in plants. Thus, bioinformatics studies using different programs and databases were conducted to predict their corresponding localization sites, nuclear export signal, nuclear localization signal, as well as expression patterns. We also found new conserved domains in most of the RPD3/HDA1 histone deacetylases which were similarly conserved in its corresponding orthologues. Assessing gene expression patterns using Genevestigator, it appears that RPD3/HDA1 histone deacetylases are expressed all throughout the plant parts and developmental stages of the plant. Conclusion: The RPD3/HDA1 histone deacetylase family in plants is divided into three distinct groups namely, Class I, Class II, and Class IV suggesting functional diversification. Class II comprises not only AtHDA5, AtHDA15, and AtHDA18 but also includes AtHDA8 and AtHDA14. New conserved domains have also been identified in most of the RPD3/HDA1 family indicating further versatile roles other than histone deacetylation.

Class II histone deacetylases in humans and other model organisms undergo nucleocytoplasmic shuttling. This unique functional regulatory mechanism has been well elucidated in eukaryotic organisms except in plant systems. In this study, we have paved the baseline evidence for the cytoplasmic and nuclear localization of Class II HDAs as well as their mRNA expression patterns. RT-PCR analysis on the different vegetative parts and developmental stages reveal that Class II HDAs are ubiquitously expressed in all tissues with minimal developmental specificity. Moreover, stable and transient expression assays using HDA-YFP/GFP fusion constructs indicate cytoplasmic localization of HDA5, HDA8, and HDA14 further suggesting their potential for nuclear transport and deacetylating organellar and cytoplasmic proteins. Organelle markers and stains confirm HDA14 to abound in the mitochondria and chloroplasts while HDA5 localizes in the ER. HDA15, on the other hand, shuttles in and out of the nucleus upon light exposure. In the absence of light, it is exported out of the nucleus where further re-exposition to light treatments signals its nuclear import. Unlike HDA5 which binds with 14-3-3 proteins, HDA15 fails to interact with these chaperones. Instead, HDA15 relies on its own nuclear localization and export signals to navigate its subcellular compartmentalization classifying it as a Class IIb HDA. Our study indicates that nucleocytoplasmic shuttling is indeed a hallmark for all eukaryotic Class II histone deacetylases.

Multiplicity of acquired cross-resistance in paclitaxel-resistant cancer cells is associated with feedback control of TUBB3 via FOXO3a-mediated ABCB1 regulation

Mercury-binding peptides from roots, stems, and leaves of Hg-treated Chromolaena odorata plants were isolated and partially characterized using RP-HPLC and ESI-MS. Upon exposure of C. odorata plants to high concentrations of 1.0 and 2.0 μᴍ Hg(NO₃)₂ treatments from 0-28 days, they accumulated as much as 125 mg/g (dry wt) Hg in the roots, 15.280 mg/g (dry wt) Hg in the stems, and 0.800 mg/g (dry wt) Hg in the leaves indicating that C. odorata has a high potential as a phytoremediation agent of inorganic mercury. The plant’s ability to accumulate and sequester Hg ions was primarily attributed to the production of Hgbinding peptides, which were initially detected through the use of Ellman’s reagent. Isolation techniques using RP-HPLC equipped with a C18 column manifested a single prominent peak consistently appearing at a retention time of 2.6-2.8 min in all the plant samples treated with different Hg concentrations at varying lengths of exposure. Further characterization of this prominent peak using electrospray ionization mass spectrometry revealed the presence of a peptide containing several cysteine residues with the highest peak concentration recorded at 91 mV and 89 mV in roots and stems of plants treated with 2.0 μᴍ Hg(NO₃)₂ for 4 wk (P < 0.05) and 85 mV in leaves treated with 1.0 μᴍ Hg(NO₃)₂ for 1 wk.

Alinsug MV, Estandarte MHG, Somodio EMN, Sabarita MJJ, Deocaris CC. 2021. Biodiversity of ethnomedicinal plants from the B’laan Tribe in Mount Matutum Protected Landscape, Southern Mindanao, Philippines. Biodiversitas 23: 554-563. Mount Matutum Protected Landscape (MMPL) is one of the key biodiversity areas in Mindanao Island, Philippines, and is part of the ancestral domains of 18 indigenous peoples. The present study aims to establish a comprehensive inventory of the medicinal flora at MMPL according to the traditional healing practices of the B'laan, a tribal community whose cultural heritage is anchored to their interactions with nature and with a rich and understudied ethnomedicinal system. Focus group discussions and key informant interviews of the tribal healers from five tribal communities revealed 101 medicinal plants belonging to 33 families were identified. The plant species have therapeutic uses for 19 disease categories. Roots and leaves are the most utilized parts which are made into a decoction, the most common preparation for oral intake. Tawal-ulad (Lunasia amara Blanco), which is used as a treatment for snake bites, dengue, dysmenorrhea, constipation, rabies, and hypertension has the highest use value (UV). Informant Consensus Factor (ICF) analysis revealed that cholera, scabies, viral infections, warts, beriberi, diabetes, gastric ulcer are the most common diseases treated with medicinal plants by the B'laan tribal healers. The biodiversity of medicinal plants, although some remain unidentified at the species level, reflects the centuries-old ethnomedicinal knowledge of the B'laan Tribe. Our study is the first comprehensive documentation of the ethnomedicinal knowledge of the B'laan Tribe residing at MMPL.