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Female germline cells in flowering plants differentiate from somatic cells to produce specialized reproductive organs, called ovules, embedded deep inside the flowers. We investigated the molecular basis of this distinctive developmental program by performing single-cell RNA sequencing (scRNA-seq) of 16,872 single cells of Arabidopsis thaliana ovule primordia at three developmental time points during female germline differentiation. This allowed us to identify the characteristic expression patterns of the main cell types, including the female germline and its surrounding nucellus. We then reconstructed the continuous trajectory of female germline differentiation and observed dynamic waves of gene expression along the developmental trajectory. A focused analysis revealed transcriptional cascades and identified key transcriptional factors that showed distinct expression patterns along the germline differentiation trajectory. Our study provides a valuable reference dataset of the transcriptional process during female germline differentiation at single-cell resolution, shedding light on the mechanisms underlying germline cell fate determination. Zhimin Hou, Yanhui Liu et al. used single cell RNA-seq to analyze the model organism, Arabidopsis thaliana, at three stages during female germline differentiation. They reconstructed the continuous trajectory of female germline differentiation, providing a valuable reference for future investigation of germline cell fate determination in A. thaliana. [ABSTRACT FROM AUTHOR]

RNA-dependent RNA polymerases (RDRs), involved in the production of various small interfering RNA (siRNA), play critical roles in plant growth, development process, and abiotic/biotic stresses. In this study, 5 RDR genes (AcRDRs) were identified from the pineapple genome. Phylogenetic analysis showed that AcRDRs could be divided into 4 subgroups. Gene structure analysis showed that the number of introns varied from 2 to 18. Furthermore, we analyzed AcRDR expression patterns in vegetative organs and in sexual organs, namely ovules and stamens, at different developmental stages respectively. AcRDR2, AcRDR3 and AcRDR6b showed higher expressions in the male and female reproductive organs, while AcRDR3 also was accumulated highly in sepal and fruit. AcRDR6a exhibited the highest expression levels at the mature ovule and stamen. AcRDR1 had an expression peak in the root. Furthermore, we checked the responses of AcRDRs to abiotic stresses and phytohormones. The results of this study provided basic genomic information for AcRDRs and insights into the probable roles of these genes in plant growth and development. [ABSTRACT FROM AUTHOR]

Auxin response factors (ARFs) are transcription factors that bind with auxin response elements to regulate the expression of auxin responsive genes. The ARF genes family is characterized by a large multigene family in plants and plays important roles in plant development. However, the ARF gene family has not yet been identified in pineapple, one of the most important tropical fruit in the world. In this study, a total of 20 ARF genes, named as AcoARF1 to AcoARF20, were identified in pineapple. Firstly, a comprehensive bioinformatics analysis of the AcoARF gene family was presented, including chromosomal locations, phylogenetic relationships, gene structures, conserved motifs. Furthermore, we analyzed AcoARF expression patterns in vegetative organs and in sexual organs, namely ovules and stamens, at 7 and 4 different developmental stages respectively. AcoARF1, AcoARF3, AcoARF7 and AcoARF8 showed higher expression in fruit. AcoARF9 and AcoARF11 exhibited higher expression in flower, leaf and fruit, but not in root. During female and male gametophyte developments, AcoARF1, AcoARF2 and AcoARF19 were expressed at high level in developing ovule and stamen, implying their critical roles in reproduction. While, some AcoARFs expressed in ovule or stamen at specific stages, indicating their potentially particular functions. Our study provides comprehensive information of ARF family in pineapple, which will be useful in directing of selection of candidate genes related to tissue development in pineapple and pave the way to further functional verification of these AcoARF genes. [ABSTRACT FROM AUTHOR]

Biofouling is an important factor that affects the bivalve farming industry. Fouling organisms may reduce growth and survival rate of the cultured species. Fouler are often filter feeders, so they are potential competitors for food resource with the cultured species. The present study was conducted to measure the impact of fouling on food uptake and nutrient release in April and June, 2006 in Daya Bay near Guangzhou, China. Results showed that fouling organisms had significant effect on food uptake and nutrient release. The chlorophyll a uptake rate of fouled scallops was 7.53Lh−1±1.416Lh−1 and 11.94Lh−1±2.497Lh−1 in April and June, respectively, significantly higher than those of cleaned scallops, i.e., 4.23Lh−1±2.744Lh−1 and 2.57Lh−1±1.832Lh−1 respectively. The consumption of total particulate matter by fouled scallops in April and June was 5.52Lh−1±0.818Lh−1 and 3.07Lh−1±0.971Lh−1, respectively; the corresponding results for cleaned scallops are 2.49Lh−1±0.614Lh−1 and 2.37±1.214Lh−1, respectively. Fouling increased ammonia release significantly. The ammonia release rate of fouled scallops was 33.81Lh−1±7.699Lh−1 and 76.39Lh−1±9.251Lh−1 in April and June, while cleaned scallops released 2.46Lh−1±0.511Lh−1 and 7.23Lh−1±1.026Lh−1 ammonia, respectively. Phosphate release of fouled scallops was 22.72Lh−1±9.978Lh−1 in June and cleaned scallops released phosphate 6.01Lh−1±0.876Lh−1 in April. Therefore, fouling contributed much to food reduction and concentration increase of ammonia and phosphate in water. [ABSTRACT FROM AUTHOR]