We studied the ethylene-insensitive, hypernodulating mutant, sickle (skl), to investigate the interaction of ethylene with auxin transport during root nodulation in Medicago truncatula. Grafting experiments demonstrated that hypernodulation in skl is root controlled. Long distance transport of auxin from shoot to root was reduced by rhizobia after 24 h in wild type but not in skl. Similarly, the ethylene precursor 1-amino cyclopropane-1-carboxylic acid inhibited auxin transport in wild type but not in skl. Auxin transport at the nodule initiation zone was significantly reduced by rhizobia after 4 h in both wild type and skl. After 24 h, auxin transport significantly increased at the nodule initiation zone in skl compared to wild type, accompanied by an increase in the expression of the MtPIN1 and MtPIN2 (pin formed) auxin efflux transporters. Response assays to different auxins did not show any phenotype that would suggest a defect of auxin uptake in skl. The auxin transport inhibitor N-1-naphthylphtalamic acid inhibited nodulation in wild type but not skl, even though N-1-naphthylphtalamic acid still inhibited auxin transport in skl. Our results suggest that ethylene signaling modulates auxin transport regulation at certain stages of nodule development, partially through PIN gene expression, and that an increase in auxin transport relative to the wild type is correlated with higher nodule numbers. We also discuss the regulation of auxin transport in skl in comparison to previously published data on the autoregulation mutant, super numerary nodules (van Noorden et al., 2006).

The interactions between two groups of rice endophytic bacterial strains and several rice cultivars were investigated. Various strains of Rhizobium leguminosarum bv. trifolii, originally isolated from rice plants grown in Egypt, comprise one group. The second group of bacterial strains was isolated from rice cultivars grown in the Philippines. Inoculation experiments with rice seedlings showed that specific isolates of these rice-associating bacteria could either promote, inhibit, or have no influence on rice plant growth. Furthermore, these growth effects were greatly influenced by the environmental growth conditions used. Studies to examine root colonisation patterns, using Rhizobium strains into which a plasmid expressing the green fluorescent protein has been placed, showed that the bacteria preferentially colonise rice seedling surfaces mainly in clumps. This occurs along grooves on the rice root surface, or at the emerging lateral root zones and at the root tips. However, rhizobia could also colonise intercellularly in lateral roots formed on the main roots near the culm region of the seedling. Under the growth conditions used, this occurred most frequently with strain R4 which multiplied and migrated to form long lines of individual bacterial cells along the inside of growing lateral roots. A bioassay to measure bacterial multiplication in rice leaves showed that the rice-associating strains can multiply and survive at different rates within these tissues. They were not, however, detected migrating into other parts of the leaf from the original site of pressure-infiltration, indicating that the bacterial ability to migrate within the lateral roots is not matched by a similar capacity in rice leaves. We suggest that some of these rice-associating bacteria possess important genes that enhance their ability to intimately colonise niches on and within rice tissues, and promote rice plant growth.

Ethylene has been hypothesised to be a regulator of root nodule development in legumes, but its molecular mechanisms of action remain unclear. The skl mutant is an ethylene-insensitive legume mutant showing a hypernodulation phenotype when inoculated with its symbiont Sinorhizobium meliloti. We used the skl mutant to study the ethylene-mediated protein changes during nodule development in Medicago truncatula. We compared the root proteome of the skl mutant to its wild-type in response to the ethylene precursor aminocyclopropane carboxylic acid (ACC) to study ethylene-mediated protein expression in root tissues. We then compared the proteome of skl roots to its wild-type after Sinorhizobium inoculation to identify differentially displayed proteins during nodule development at 1 and 3 days post inoculation (dpi). Six proteins (pprg-2, Kunitz proteinase inhibitor, and ACC oxidase isoforms) were down-regulated in skl roots, while three protein spots were up-regulated (trypsin inhibitor, albumin 2, and CPRD49). ACC induced stress-related proteins in wild-type roots, such as pprg-2, ACC oxidase, proteinase inhibitor, ascorbate peroxidase, and heat-shock proteins. However, the expression of stress-related proteins such as pprg-2, Kunitz proteinase inhibitor, and ACC oxidase, was down-regulated in inoculated skl roots. We hypothesize that during early nodule development, the plant induces ethylene-mediated stress responses to limit nodule numbers. When a mutant defective in ethylene signaling, such as skl, is inoculated with rhizobia, the plant stress response is reduced, resulting in increased nodule numbers.

Most rhizobial strains inhibit rice root growth in the presence of calcium or potassium nitrates, but not ammonium nitrate. Certain rhizobial strains, however, such as strain R4, do not inhibit rice growth and can enter rice roots and multiply in the intercellular spaces. By using the green fluorescent protein (GFP) as a visual marker, it was found that Rhizobium became intimately associated with rice seedling roots within 24-48 h. During this initial period it was observed that strain R4 could cause structural changes resembling infection threads within the rice root hairs. Generally, the sites of the emerging lateral roots provide a temporary entry point for rhizobia, either by root hair entry or crack entry. All tested GFP-labelled Rhizobium strains infected the root hairs near the base of growing lateral roots. This study suggests that some strains may have the ability to infect rice root tissues via root hairs located at the emerging lateral roots and to spread extensively throughout the rice root.

Teknologi fotobioreaktor mikroalga untuk penangkapan karbon merupakan teknologi yang mengandalkanproses fotosintesis untuk memfiksasi gas CO2 dan mengkonversinya menjadi biomassa. Faktor utamayang mempengaruhi proses pertumbuhan, fiksasi karbon dan produksi biomassa adalah jenis mikroalga,gas CO2, nutrisi, cahaya, suhu, pH dan pengadukan. Untuk aplikasi teknologi ini dalam skala besar,selain faktor-faktor tersebut di atas, karakteristik pertumbuhan mikroalga tertentu dan pemanenannyaperlu diketahui untuk mendapatkan hasil yang maksimum. Hingga saat ini masih sedikit informasi yangdiperoleh tentang karakteristik pertumbuhan dan produksi biomassa dari mikroalga dalam fotobioreaktoryang dipanen dengan sistem semi-kontinu dan sistem kontinu. Tujuan dari tulisan ini adalah membahastentang pola pertumbuhan sel-sel mikroalga dalam fotobioreaktor yang berkaitan dengan strategipemanenan sistem batch, semi-kontinu dan kontinu, dan untuk menentukan sistem yang lebih cocokditerapkan di Indonesia. Berdasarkan kelebihan dan kekurangan dari masing-masing sistem, pemanenansistem semi-kontinu menjadi pilihan utama untuk aplikasi fotobioreaktor mikroalga penangkap karbon diIndonesia.

This paper originates from an address at the 8th International Symposium on Nitrogen Fixation with Non-Legumes, Sydney, NSW, December 2000 We examined growth responses of rice seedlings (Oryza sativaL. cv. Pelde) to specific Rhizobium strains and their mutants, to investigate the molecular basis of colonization and the stimulation or inhibition of rice growth and development by rhizobia. Inoculation experiments with rice seedlings showed that specific Rhizobium isolates of these rice-associated and legume-associated rhizobia could either promote, inhibit, or have no influence on rice plant growth. There are genes on certain plasmids of Rhizobium leguminosarum bv. trifolii and R. leguminosarum bv. viciae that affect the growth and development of rice root morphology. Additionally, we found that bacteria can intimately associate with, and enter into, rice seedling roots by alternative mechanisms to those encoded by the symbiotic (pSym) and the tumour-inducing (Ti) plasmids. Investigations suggest an involvement of the phytohormone auxin, and possibly nitrate, in this complex rice–Rhizobium interaction.

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Abstract-In indonesia, a substantial waste cooking oil from households is being disposed to drainage and soil, according to the recent survey conducted in bogor, causing environmental damages of water and soil pollutions, as well as increase in ghg emission. in urban areas of Japan, waste cooking oil is mostly being solidified and disposed as incinerating waste, whereas in local areas, it is being disposed into drainage and causing sewage system deterioration.The waste cooking oil recycling programs conducted by Bogor and Niigata cities were reviewed highlighting environmental and economical issues. Similarities were found, in total waste cooking oil amounts collected, and the 60% ratio of total recycled bio diesel fuel for their vehicle operations.Life cycle impacts in GHG emission of cooking oil were estimated using operationaldata of a factory as well as reported data of LCA studies. The environmental advantage of the waste cooking oil recycling, compared with the drainage and soil disposals as well as the complete use, did not necessarily encourage the recycling activities, due to economical and technical constraints, the latter case in the Bogor City seems to be easily overcome, than the issues of high labour costs in Japan.