Cloning of Three Antiporter Genes from Arabidopsis and Rice for Over-Expressing Them in Farmer Popular Tomato Varieties of Bangladesh

Salinity is one of the most critical environmental problems, which causes plant growth retardation by disturbing intracellular ion homeostasis. The Na+/H+ antiporter plays an important role in resistance to salt stress by sequestering Na+ in exchange for H+ across the vacuolar membranes. In the current study, the coding regions of two Arabidopsis antiporters (AtNHX1 and AtNHX2) and one rice antiporter (OsNHX1) were amplified by target specific PCR. PCR amplicons were first cloned into pENTR/D-TOPO and later recombined with a destination vector (pK7WG2.0) by LR reaction. Positive clones were selected by PCR, restriction digestion (RD) and sequencing. They were then transformed into Agrobacterium tumefaciens (LBA4404 strain) for subsequent transformation of farmer popular tomato varieties.

Characterization of an ethylene receptor homolog gene from rice

Ethylene plays important roles in plant growth, development and stress responses. Its receptor genes have been studied in dicots such as Arabidopsis, tobacco and tomato. However, no research has been reported for the ethylene receptors from monocots currently. In the present study, we cloned an ethylene receptor gene OSPK2 from rice and found that its encoded protein was divergent from the ethylene receptors from dicots. OSPK2 had a long extension in its N- terminal, followed by three transmembrane segments, a GAF domain, a putative kinase domain and a putative receiver domain. Although most of the domains were conserved, the expected phosphorylation site His and the phosphate receiver Asp have been replaced by Gln and Asn, respectively. This fact indicates that OSPK2 may not function as a histidine kinase in a phosphorelay manner, but rather play roles by other mechanism, probably through Ser/Thr kinase activity. The expression of the OSPK2 gene was investigated by RT-PCR method under different conditions. We found that this gene was apparently induced by wounding and PEG treatment, but not significantly affected by salt and ABA treatments. The differential expression of the OSPK2 gene may reflect its roles in mediating different abiotic stress responses, consistent with our previous studies on tobacco ethylene receptors.

Tobacco two-component gene NTHK2

By using a previously isolated tobacco two-component gene NTHK1 as a probe, we screened a cDNA library and obtained a homologous gene designated NTHK2. Sequencing analysis revealed that NTHK2 encoded a putative ethylene receptor homolog and contained a histidine kinase domain and a receiver domain. In the histidine kinase domain, the histidine at the phosphorylation site was replaced by an asparagine. Southern analysis indicated that NTHK2 was present at low copies in tobacco genome. The expression of NTHK2 was studied using a competitive RT-PCR method. It was found that, in young flower buds, NTHK2 was expressed abundantly, while in other organs or tissues, it was expressed in a low level. When leaf was subjected to wounding (cutting) treatment, NTHK2 expression was increased. When tobacco seedlings were stressed with PEG and heat shock, NTHK2 transcription was also enhanced. Other treatments showed little effects. These results indicated that NTHK2 might be involved in the developmental processes and

Performance index: An expeditious tool to screen for improved drought resistance in the Lathyrus genus

Some species of the Lathyrus genus are among the most promising crops for marginal lands, with high resilience to drought, flood, and fungal diseases, combined with high yields and seed nutritional value. However, lack of knowledge on the mechanisms underlying its outstanding performance and methodologies to identify elite genotypes has hampered its proper use in breeding. Chlorophyl a fast fluorescence transient （JIP test）, was used to evaluate water deficit （WD） resistance in Lathyrus genus. Our results reveal unaltered photochemical values for al studied genotypes showing resistance to mild WD. Under severe WD, two Lathyrus sativus genotypes showed remarkable resilience maintaining the photochemical efficiency, contrary to other genotypes studied. Performance index （PIABS） is the best parameter to screen genotypes with improved performance and grain production under WD. Moreover, we found that JIP indices are good indicators of genotypic grain production under WD. Quantum yield of electron transport （wEo） and efficiency with which＆trapped excitons can move electrons further than QA （c0） revealed as important traits related to improved photosyn-thetic performance and should be exploited in future Lathyrus germplasm improvements. The JIP test herein described showed to be an expeditious tool to screen and to identify elite genotypes with improved drought resistance.