Suberin deficiency and its effect on the transport physiology of young poplar roots.

The precise functions of suberized apoplastic barriers in root water and nutrient transport physiology have not fully been elucidated. While lots of research has been performed with mutants of Arabidopsis, little to no data are available for mutants of agricultural crop or tree species. By employing a combined set of physiological, histochemical, analytical, and transport physiological methods as well as RNA-sequencing, this study investigated the implications of remarkable CRISPR/Cas9-induced suberization defects in young roots of the economically important gray poplar. While barely affecting overall plant development, contrary to literature-based expectations significant root suberin reductions of up to 80-95% in four independent mutants were shown to not evidently affect the root hydraulic conductivity during non-stress conditions. In addition, subliminal iron deficiency symptoms and increased translocation of a photosynthesis inhibitor as well as NaCl highlight the involvement of suberin in nutrient transport physiology. The multifaceted nature of the root hydraulic conductivity does not allow drawing simplified conclusions such as that the suberin amount must always be correlated with the water transport properties of roots. However, the decreased masking of plasma membrane surface area could facilitate the uptake but also leakage of beneficial and harmful solutes.

OPDAT1, a plastid envelope protein involved in 12-oxo-phytodienoic acid export for jasmonic acid biosynthesis in Populus.

Twelve-oxo-phytodienoic acid (OPDA), the cyclopentenone precursor of jasmonic acid (JA), is required for the wounding response of plants. OPDA is derived from plastid-localized α-linolenic acid (α-LeA; 18:3) via the octadecanoid pathway, and is further exported from plastids to the cytosol for JA biosynthesis. However, the mechanism of OPDA transport from plastids has yet to be elucidated. In the current study, a plastid inner envelope-localized protein, designated 12-oxo-Phtyodienoic Acid Transporter 1 (OPDAT1), was identified and shown to potentially be involved in OPDA export from plastids, in Populus trichocarpa. Torr. OPDAT1 is expressed predominantly in young leaves of P. trichocarpa. Functional expression of OPDAT1 in yeast cells revealed that OPDAT1 is involved in OPDA transport. Loss-of-function of OPDAT1 in poplar resulted in increased accumulation of OPDA in the extracted plastids and a reduction in JA concentration, whereas an OPDAT1-overexpressing line showed a reverse tendency in OPDA accumulation and JA biosynthesis. OPDAT1 transcripts were rapidly induced by mechanical wounding of leaves, and an opdat1 mutant transgenic plant displayed increased susceptibility to spider mite (Tetranychus urticae) infestation. Collectively, these data suggest that OPDAT1 is an inner envelope transporter for OPDA, and this has potential implications for JA biosynthesis in poplar under environmental stresses.

Two Plastid Fatty Acid Exporters Contribute to Seed Oil Accumulation in Arabidopsis.

Triacylglycerols (TAGs) are the major storage form of seed oil in oilseed plants. They are biosynthesized de novo in seed plastids and then transported into the endoplasmic reticulum. However, the transport mechanism for plastid fatty acids in developing seeds remains unknown. Here, we isolated two novel plastid fatty acid exporters (FATTYACID EXPORT 2 [FAX2] and FAX4, respectively) specifically abundant in seed embryos during the seed-filling stage in Arabidopsis (Arabidopsis thaliana). FAX2 and FAX4 were both localized to the chloroplast membrane. FAX2 and FAX4 loss-of-function mutations caused deficiencies in embryo and cotyledon development. Seeds of fax2fax4 double mutants exhibited significantly reduced TAG contents but elevated levels of plastid lipid contents compared with those of wild-type plants. By contrast, overexpression of FAX2 or FAX4 enhanced TAG deposition. Seed-feeding experiments showed that the two FAX proteins transported 14C-plastid fatty acids and 13C-oleic acids for TAG biosynthesis during the seed-filling stage. Together, our data demonstrate that FAX2 and FAX4 play critical roles in transporting plastid fatty acids for TAG biosynthesis during seed embryo development. These two transporters may have broad application for increasing oil yield in oilseed crops.

Characterization of Fatty Acid Exporters involved in fatty acid transport for oil accumulation in the green alga Chlamydomonas reinhardtii.

BACKGROUND: In the past few decades, microalgae biofuel has become one of the most interesting sources of renewable energy. However, the higher cost of microalgae biofuel compared to that of petroleum prevented microalgae biofuel production. Therefore, the research on increasing lipid productivity from microalgae becomes more important. The lipid production source, triacylglycerol biosynthesis in microalgae requires short chain fatty acids as substrates, which are synthesized in chloroplasts. However, the transport mechanism of fatty acids from microalgae chloroplasts to cytosol remains unknown. RESULTS: cDNAs from two homologs of the Arabidopsis fatty acid exporter 1 (FAX1) were cloned from Chlamydomonas reinhardtii and were named crfax1 and crfax2. Both CrFAXs were involved in fatty acid transport, and their substrates were mainly C16 and C18 fatty acids. Overexpression of both CrFAXs increased the accumulation of the total lipid content in algae cells, and the fatty acid compositions were changed under normal TAP or nitrogen deprivation conditions. Overexpression of both CrFAXs also increased the chlorophyll content. The MGDG content was decreased but the TAG, DAG, DGDG and other lipid contents were increased in CrFAXs overexpression strains. CONCLUSION: These results reveal that CrFAX1 and CrFAX2 were involved in mediating fatty acid export for lipids biosynthesis in C. reinhardtii. In addition, overexpression of both CrFAXs obviously increased the intracellular lipid content, especially the triacylglycerol content in microalgae, which provides a potential technology for the production of more biofuels using microalgae.

Genome-wide analysis of MATE transporters and molecular characterization of aluminum resistance in Populus.

Ionic aluminum (Al) in acidic soils, comprising approximately 50% of arable land globally, is highly toxic to most plant species. Populus grow naturally in acidic soils and tolerate high concentrations of Al. Multidrug and toxic compound extrusion (MATE) family genes in plants are involved in responses to Al tolerance. To date, however, the functional roles of the MATE genes in Populus remain unclear. In the present study, 71 putative MATE transporters were predicted in the genome of Populus trichocarpa. The chromosome distribution, phylogenetic relationships, and expression level analysis revealed that four candidate MATE genes belonging to subgroup IIIc might contribute to high Al tolerance in poplar. Further, the expression levels of two subgroup IIIc members, PtrMATE1 and PtrMATE2, were induced by Al stress. Transient expression in onion epidermal cells showed that PtrMATE1 was localized to the plasma membrane. Overexpression of PtrMATE1 increased Al-induced secretion of citrate from the root apex of transgenic plants. Al-induced inhibition of root growths were alleviated in both PtrMATE1 overexpression lines in Populus and in Arabidopsis compared with wild-type plants. In addition, PtrMATE1 expression was induced at 12 h after exposure to Al stress whereas PtrMATE2 expression was induced at 24 h, indicating that these proteins coordinately function in response to Al stress in poplar. Taken together, these results provide important insights into the molecular mechanisms involved in Al tolerance in poplar.

Reduced-order model based active disturbance rejection control of hydraulic servo system with singular value perturbation theory.

Hydraulic servomechanism is the typical mechanical/hydraulic double-dynamics coupling system with the high stiffness control and mismatched uncertainties input problems, which hinder direct applications of many advanced control approaches in the hydraulic servo fields. In this paper, by introducing the singular value perturbation theory, the original double-dynamics coupling model of the hydraulic servomechanism was reduced to a integral chain system. So that, the popular ADRC (active disturbance rejection control) technology could be directly applied to the reduced system. In addition, the high stiffness control and mismatched uncertainties input problems are avoided. The validity of the simplified model is analyzed and proven theoretically. The standard linear ADRC algorithm is then developed based on the obtained reduced-order model. Extensive comparative co-simulations and experiments are carried out to illustrate the effectiveness of the proposed method.