Selenium Fractionation and Speciation in Paddy Soils and Accumulation in Rice Under Field Conditions in Jinhua Zhejinang Province, China

Soils, as well as paddy tissue samples, were collected in the Se-rich area of Jinhua County, Zhejiang Province, China. Sequential extraction procedure was used for selenium (Se) fractionation, including soluble Se, exchangeable Se, carbonate-bound Se, iron and manganese oxide-bound Se, humic acids-bound Se, organic matter-bound Se, and the residual Se fraction. The results showed that soluble Se, exchangeable Se, carbonate-bound Se, iron and manganese oxide-bound Se fractions accounted for less than 2% of the total Se, respectively. Organic matter-bound Se was the dominant fractions. The average concentrations (mg kg−1) of Se in the paddy tissues were 0.069 in seed, 0.263 in root, 0.09 in stalk, and 0.17 in leaf. The organic matter-bound Se had a significant indirect effect on Se accumulation in paddy tissues. In conclusion, organic matter-bound Se was an important fraction and source of plant Se in agricultural soil

MaHAK5, a Potassium Transporter of Banana, Enhanced Potassium Uptake in Transgenic <i>Arabidopsis</i> under Low Potassium Conditions

Potassium (K+) is one of the most important macronutrients for plant growth and development. It is generally accepted that the KUP/HAK/KT transporters play essential roles in K+ uptake at low concentrations. However, their physiological functions in bananas remain unknown. Here, we cloned MaHAK5 and analyzed its functions in banana (Musa acuminata). Gene expression analysis showed that MaHAK5 was upregulated in the roots and leaves in the early stage of low K+ (LK) stress. MaHAK5 was localized in the cytomembrane. The expression of MaHAK5 improved the growth of the low K+-sensitive yeast mutant R5421 at different K+ supply levels. Overexpression of MaHAK5 in Arabidopsis thaliana significantly enhanced the ability for K+ uptake and increased the chlorophyll content under LK stress. These results indicate that MaHAK5 plays a crucial role in maintaining K+ uptake in bananas

The M35 Metalloprotease Effector FocM35_1 Is Required for Full Virulence of Fusarium oxysporum f. sp. cubense Tropical Race 4

Fusarium oxysporum f. sp. cubense tropical race 4 (Foc TR4) causes Fusarium wilt of banana, the most devastating disease on a banana plant. The genome of Foc TR4 encodes many candidate effector proteins. However, little is known about the functions of these effector proteins on their contributions to disease development and Foc TR4 virulence. Here, we discovered a secreted metalloprotease, FocM35_1, which is an essential virulence effector of Foc TR4. FocM35_1 was highly upregulated during the early stages of Foc TR4 infection progress in bananas. The FocM35_1 knockout mutant compromised the virulence of Foc TR4. FocM35_1 could interact with the banana chitinase MaChiA, and it decreased banana chitinase activity. FocM35_1 induced cell death in Nicotiana benthamiana while suppressing the INF1-induced hypersensitive response (HR), and its predicted enzymatic site was required for lesion formation and the suppression to INF1-induced HR on N. benthamiana leaves. Importantly, treatment of banana leaves with recombinant FocM35_1 accelerates Foc TR4 infection. Collectively, our study provides evidence that metalloprotease effector FocM35 seems to contribute to pathogen virulence by inhibiting the host immunity

RFRP-3 Influences Apoptosis and Steroidogenesis of Yak Cumulus Cells and Compromises Oocyte Meiotic Maturation and Subsequent Developmental Competence

RF amide-related peptide 3 (RFRP-3), a mammalian ortholog of gonadotropin-inhibitory hormone (GnIH), is identified to be a novel inhibitory endogenous neurohormonal peptide that regulates mammalian reproduction by binding with specific G protein-coupled receptors (GPRs) in various species. Herein, our objectives were to explore the biological functions of exogenous RFRP-3 on the apoptosis and steroidogenesis of yak cumulus cells (CCs) and the developmental potential of yak oocytes. The spatiotemporal expression pattern and localization of GnIH/RFRP-3 and its receptor GPR147 were determined in follicles and CCs. The effects of RFRP-3 on the proliferation and apoptosis of yak CCs were initially estimated by EdU assay and TUNEL staining. We confirmed that high-dose (10−6 mol/L) RFRP-3 suppressed viability and increased the apoptotic rates, implying that RFRP-3 could repress proliferation and induce apoptosis. Subsequently, the concentrations of E2 and P4 were significantly lower with 10−6 mol/L RFRP-3 treatment than that of the control counterparts, which indicated that the steroidogenesis of CCs was impaired after RFRP-3 treatment. Compared with the control group, 10−6 mol/L RFRP-3 treatment decreased the maturation of yak oocytes efficiently and subsequent developmental potential. We sought to explore the potential mechanism of RFRP-3-induced apoptosis and steroidogenesis, so we observed the levels of apoptotic regulatory factors and hormone synthesis-related factors in yak CCs after RFRP-3 treatment. Our results indicated that RFRP-3 dose-dependently elevated the expression of apoptosis markers (Caspase and Bax), whereas the expression levels of steroidogenesis-related factors (LHR, StAR, 3β-HSD) were downregulated in a dose-dependent manner. However, all these effects were moderated by cotreatment with inhibitory RF9 of GPR147. These results demonstrated that RFRP-3 adjusted the expression of apoptotic and steroidogenic regulatory factors to induce apoptosis of CCs, probably through binding with its receptor GPR147, as well as compromised oocyte maturation and developmental potential. This research revealed the expression profiles of GnIH/RFRP-3 and GPR147 in yak CCs and supported a conserved inhibitory action on oocyte developmental competence