查看更多>>摘要：Cell wall biogenesis is required for the production of seeds of higher plants. However, little is known about regulatory mechanisms underlying cell wall biogenesis during seed formation. Here we show a role for the phosphorylation of Arabidopsis cellulose synthase 1 (AtCESA1) in modulating pectin synthesis and methylesterification in seed coat mucilage. A phosphor-null mutant of AtCESA1 on T166 (AtCESA1T(166A)) was constructed and introduced into a null mutant of AtCESA1 (Atcesa1-1). The resulting transgenic lines showed a slight but significant decrease in cellulose contents in mature seeds. Defects in cellulosic ray architecture along with reduced levels of non-adherent and adherent mucilage were observed on the seeds of the AtCESA1T(166A )mutant. Reduced mucilage pectin synthesis was also reflected by a decrease in the level of uronic acid. Meanwhile, an increase in the degree of pectin methylesterification was also observed in the seed coat mucilage of AtCESA1T(166A) mutant. Change in seed development was further reflected by a delayed germination and about 50% increase in the accumulation of proanthocyanidins, which is known to bind pectin and inhibit seed germination as revealed by previous studies. Taken together, the results suggest a role of AtCESA1 phosphorylation on T166 in modulating mucilage pectin synthesis and methylesterification as well as cellulose synthesis with a role in seed development.
查看更多>>摘要：The importance of the evolutionarily conserved Argonaute (AGO) proteins has been well recognized for their involvement in the RNA interference pathways. Recent discoveries in animals demonstrated that AGOs also participate in alternative splicing (AS). Motivated by the question whether the AGO proteins are also functional in RNA splicing in plants, we searched for the introns excised through an AGO-dependent manner in Arabidopsis (Arabidopsis thaliana). RNA sequencing (RNA-seq) data analysis uncovered hundreds of the introns up-or down-regulated in the ago1 and ago4 mutants, respectively. For different genes, AGOs might play either a positive or a negative role in intron excision, which was further validated by reverse transcription-polymerase chain reaction (RT-PCR). Some introns were specifically regulated by one of the AGO proteins, while some were regulated by both AGOs. Besides, a large portion of the AGO-dependent introns were organ-specifically regulated. RNA immunoprecipitation combined with high-throughput sequencing (RIP-seq) revealed that both AGOs preferen-tially bound to the intronic regions, supporting their high intron binding affinities. Immunoprecipitation fol-lowed by mass spectrometry (IP-MS) was performed to identify the proteins potentially interacting with the two AGOs. Six novel interactors (two interacting with AGO1 and four with both AGOs) involved in mRNA binding were uncovered, which might facilitate AGO-intron recognition. Analysis of the RNA-seq data from the rice (Oryza sativa) ago18 mutants revealed that hundreds of the introns were expressed in an AGO18-dependent manner. In summary, our results point to the novel role of the plant AGOs in intron splicing, paving a way for further studies on the mechanisms underlying AGO-mediated RNA splicing.
查看更多>>摘要：FERONIA (FER) is a membrane-localized receptor-like kinase that plays pivotal roles in male and female gametophyte recognition, hormone signaling crosstalk, and biotic and abiotic responses. Most reports focus on the functions of FER in model plant Arabidopsis thaliana. However, the functions of FER homologs have not been deeply investigated in apple (Malus domestica), an important economic fruit crop distributed worldwide, especially in China. In this study, we identified an apple homolog of Arabidopsis FER, named MdFER (MDP0000390677). The two proteins encoded by AtFER and MdFER share similar domains: an extracellular malectin-like domain, a transmembrane domain, and an intracellular kinase domain. MdFER was further proven to localize to the plasma membrane in the epidermal cells of Nicotiana benthamiana. MdFER was widely expressed in different apple tissues, but the highest expression was found in roots. In addition, expression of MdFER was significantly induced by treatment with abscisic acid (ABA) and salt (NaCl). Overexpressing MdFER dramatically improved the resistance to salt stress and reduced the sensitivity to ABA in apple callus, while suppressing MdFER expression showed contrary effects. Furthermore, ectopic expression of MdFER in Arabidopsis significantly increased the salt tolerance and reduced the sensitivity to ABA. In addition, under salt stress and ABA treatment, Arabidopsis with highly expressed MdFER accumulated less reactive oxygen species (ROS), and the enzymatic activity of two ROS scavengers, superoxide dismutase and catalase, was higher compared with that of wild type (WT). Our work proves that MdFER positively regulates salt tolerance and negatively regulates ABA sensitivity in apple, which enriched the functions of FER in different plant species.
Pottier, MathieuSchladt, T. MoritzEjike, J. ObinnaRedzich, Laura...
17页
查看更多>>摘要：During multicellularization, plants evolved unique cell-cell connections, the plasmodesmata (PD). PD of angiosperms are complex cellular domains, embedded in the cell wall and consisting of multiple membranes and a large number of proteins. From the beginning, it had been assumed that PD provide passage for a wide range of molecules, from ions to metabolites and hormones, to RNAs and even proteins. In the context of assimilate allocation, it has been hypothesized that sucrose produced in mesophyll cells is transported via PD from cell to cell down a concentration gradient towards the phloem. Entry into the sieve element companion cell complex (SECCC) is then mediated on three potential routes, depending on the species and conditions, - either via diffusion across PD, after conversion to raffinose via PD using a polymer trap mechanism, or via a set of transporters which secrete sucrose from one cell and secondary active uptake into the SECCC. Multiple loading mechanisms can likely coexist. We here review the current knowledge regarding photoassimilate transport across PD between cells as a prerequisite for translocation from leaves to recipient organs, in particular roots and developing seeds. We summarize the state-of-the-art in protein composition, structure, transport mechanism and regulation of PD to apprehend their functions in carbohydrate allocation. Since many aspects of PD biology remain elusive, we highlight areas that require new approaches and technologies to advance our understanding of these enigmatic and important cell-cell connections.
NSTL
Elsevier