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Pollen tube tip growth requires intricate Ca2+ signaling. Recent studies have also identified rapid alkalization factor (RALF)-family peptides and their receptors as critical components for pollen tube tip growth and integrity. The functional relationship of RALF and calcium signaling modules remains largely unclear. Here we report that disruption of RALF signaling pathway abolished the cytosolic Ca2+ gradient in the pollen tube, indicating that Ca2+ signaling is downstream of the RALF signaling pathway. We identified MILDEW RESISTANCE LOCUS O (MLO) family proteins MLO1, 5, 9, 15, as Ca2+ channels required for Ca2+ influx and pollen tube integrity. We further reconstituted the biochemical pathway in which signaling via RALF and RALF receptors activated MLO1/5/9/15 calcium channels. Together, we conclude that RALF peptides derived from pollen tube bind to their receptors to establish pollen tube Ca2+ gradient through activation of the MLO channels. Our finding has thus provided a mechanistic link between the RALF signaling pathway and Ca2+ signaling in controlling pollen tube integrity and growth.

The Changjiang Estuary and adjacent East China Sea are well-known hypoxic aquatic environments. Eutrophication-driven hypoxia frequently occurs in coastal areas, posing a major threat to the ecological environment, including altering community structure and metabolic processes of marine organisms, and enhancing diversion of energy shunt into microbial communities. However, the responses of microbial communities and their metabolic pathways to coastal hypoxia remain poorly understood. Here, we studied the microbial communities collected from spatiotemporal samplings using metagenomic sequencing in the Changjiang Estuary and adjacent East China Sea. This generated 1.31 Tbp of metagenomics data, distributed across 103 samples corresponding to 8 vertical profiles. We further reported 1,559 metagenome-assembled genomes (MAGs), of which 508 were high-quality MAGs (Completeness > 90% and Contamination < 10%). Phylogenomic analysis classified them into 181 archaeal and 1,378 bacterial MAGs. These results provided a valuable metagenomic dataset available for further investigation of the effects of hypoxia on marine microorganisms. [ABSTRACT FROM AUTHOR]

Pathogen-associated molecular patterns (PAMPs) activate innate immunity in both animals and plants. Although calcium has long been recognized as an essential signal for PAMP-triggered immunity in plants, the mechanism of PAMP-induced calcium signalling remains unknown.sup.1,2. Here we report that calcium nutrient status is critical for calcium-dependent PAMP-triggered immunity in plants. When calcium supply is sufficient, two genes that encode cyclic nucleotide-gated channel (CNGC) proteins, CNGC2 and CNGC4, are essential for PAMP-induced calcium signalling in Arabidopsis.sup.3-7. In a reconstitution system, we find that the CNGC2 and CNGC4 proteins together--but neither alone--assemble into a functional calcium channel that is blocked by calmodulin in the resting state. Upon pathogen attack, the channel is phosphorylated and activated by the effector kinase BOTRYTIS-INDUCED KINASE1 (BIK1) of the pattern-recognition receptor complex, and this triggers an increase in the concentration of cytosolic calcium.sup.8-10. The CNGC-mediated calcium entry thus provides a critical link between the pattern-recognition receptor complex and calcium-dependent immunity programs in the PAMP-triggered immunity signalling pathway in plants. The cyclic nucleotide-gated channel proteins CNGC2 and CNGC4 form a calcium channel in Arabidopsis; this channel is blocked by calmodulin in the resting state but is phosphorylated and activated upon pathogen attack, triggering an increase in cytosolic calcium levels., Author(s): Wang Tian [sup.1] , Congcong Hou [sup.1] , Zhijie Ren [sup.2] , Chao Wang [sup.1] , Fugeng Zhao [sup.3] , Douglas Dahlbeck [sup.1] , Songping Hu [sup.1] , Liying [...]

Kinesin family member17 (KIF17), a homologous dimer of the kinesin-2 protein family, has important microtubule-dependent and -independent roles in spermiogenesis. Little is known about KIF17 in the mollusk, Phascolosoma esculenta, a newly developed mariculture species in China. Here, we cloned the open reading frame of Pe-kif17 and its related gene, Pe-act, and performed bioinformatics analysis on both. Pe-KIF17 and Pe-ACT are structurally conserved, indicating that they may be functionally conserved. The expression pattern of kif17/act mRNA performed during spermiogenesis revealed their expression in diverse tissues, with the highest expression level in the coelomic fluid of P. esculenta. The expressions of Pe-kif17 and Pe-act mRNA were relatively high during the breeding season (July–September), suggesting that Pe-KIF17/ACT may be involved in spermatogenesis, particularly during spermiogenesis. Further analysis of Pe-kif17 mRNA via fluorescence in situ hybridization revealed the continuous expression of this mRNA during spermiogenesis, suggesting potential functions in this process. Immunofluorescence showed that Pe-KIF17 co-localized with α-tubulin and migrated from the perinuclear cytoplasm to one side of the spermatid, forming the sperm tail. Pe-KIF17 and Pe-ACT also colocalized. KIF17 may participate in spermiogenesis of P. esculenta, particularly in nuclear reshaping and tail formation by interacting with microtubule structures similar to the manchette. Moreover, Pe-KIF17 with Pe-ACT is also involved in nuclear reshaping and tail formation in the absence of microtubules. This study provides evidence for the role of KIF17 during spermiogenesis and provides theoretical data for studies of the reproductive biology of P. esculenta. These findings are important for spermatogenesis in mollusks. [ABSTRACT FROM AUTHOR]

Mitochondria are essential for spermiogenesis. Prohibitins (PHBs; prohibitin 1, PHB1 or PHB, and prohibitin 2, PHB2) are evolutionarily conserved and ubiquitously expressed mitochondrial proteins that act as scaffolds in the inner mitochondrial membrane. In this study, we analyzed the molecular structure and dynamic expression characteristics of Ot-PHBs, observed the colocalization of Ot-PHB1 with mitochondria and polyubiquitin, and studied the effect of phb1 knockdown on mitochondrial DNA (mtDNA) content, reactive oxygen species (ROS) levels, and apoptosis-related gene expression in spermatids. Our aim was to explore the effect of Ot-PHBs on mitochondrial function during the spermiogenesis of Octopus tankahkeei (O. tankahkeei), an economically important species in China. The predicted Ot-PHB1/PHB2 proteins contained an N-terminal transmembrane, a stomatin/prohibitin/flotillin/HflK/C (SPFH) domain (also known as the prohibitin domain), and a C-terminal coiled-coil domain. Ot-phb1/phb2 mRNA were widely expressed in the different tissues, with elevated expression in the testis. Further, Ot-PHB1 and Ot-PHB2 were highly colocalized, suggesting that they may function primarily as an Ot-PHB compiex in O. tankahkeei. Ot-PHB1 proteins were mainly expressed and localized in mitochondria during spermiogenesis, implying that their function may be localized to the mitochondria. In addition, Ot-PHB1 was colocalized with polyubiquitin during spermiogenesis, suggesting that it may be a polyubiquitin substrate that regulates mitochondrial ubiquitination during spermiogenesis to ensure mitochondrial quality. To further investigate the effect of Ot-PHBs on mitochondrial function, we knocked down Ot-phb1 and observed a decrease in mtDNA content, along with increases in ROS levels and the expressions of mitochondria-induced apoptosis-related genes bax, bcl2, and caspase-3 mRNA. These findings indicate that PHBs might influence mitochondrial function by maintaining mtDNA content and stabilizing ROS levels; in addition, PHBs might affect spermatocyte survival by regulating mitochondria-induced apoptosis during spermiogenesis in O. tankahkeei. [ABSTRACT FROM AUTHOR]