Rice Genetics IV - IRRI books - International Rice Research Institute

Table 1. Fresh and dry shoot weight of R 1transgenic rice or NT (nontransformed) control plantsafter dehydration stress a or salt stress a .Fresh shoot weight (g)Dry shoot weight (g)Plasmid Dehydration Salt Dehydration Saltstress b stress c stress b stress cpJPM44 (with group 2 LEA gene PMA80) 4.8 4.7 1.05 1.02pJPM45 (with group 1 LEA gene PMA1959) 4.3 4.3 0.99 0.98NT control 3.2 3.4 0.70 0.67aR 1 plants from pJPM44-transformed plant lines were germinated. Six wk later, six plants from eachplant line (total 36 R 1 plants) were used for a dehydration-stress-tolerance experiment and 36 R 1 plantswere used for a salt-stress-tolerance experiment. Similarly, pJPM45-transformed plant lines and NTcontrols were grown and tested in the same way. b For dehydration-stress tolerance, 36 R 1 plants (fromsix plant lines) and 36 R 1 nontransgenic control plants were not watered for 8 d and then watered for 8d. Then the fresh shoot weights and dry shoot weights were measured. The average value of the 36plants was expressed as weight (g) per plant. c For salinity-stress tolerance, 36 R 1 plants grown in sixpots were placed in a tray containing 5 L water plus liquid fertilizer and 200 mM NaCl. Water was addeddaily to maintain the volume in the trays. After 9 d of salt stress, water was added to the pots directly towash out the salt. Eight days later, the fresh shoot weights and dry shoot weights of the 36 plants weremeasured and the average value was expressed as weight (g) per plant.osmoregulation and tolerance for salt and drought stress in plants (Delauney and Verma1993). Proline was believed to act as an osmoprotectant, as a sink for energy to regulateredox potentials, or as a compound that protects macromolecules from denaturation.Kavi Kishor et al (1995) demonstrated that overproduction of proline enhancedroot biomass and flower development in transgenic tobacco under water-stress conditions.Zhu et al (1998) introduced a delta 1-pyrroline-5-carboxylate synthetase (P5CS)cDNA from mothbean into rice cells by the biolistic method. Fertile transgenic riceplants were regenerated. It was found that expression of this P5CS transgene led tostress-induced overproduction of the P5CS enzyme and proline accumulation. Second-generation(R 1 ) transgenic rice plants showed an increase in biomass under saltstressand water-stress conditions compared with the nontransformed control plants.Cheng et al (2000) compared the extent of stress tolerance of transgenic rice plantsby driving the P5CS transgene expression with either a constitutive promoter or astress-inducible promoter. To test the expression of p5cs cDNA in transgenic plants,three plasmids were constructed (Fig. 1). pJS102 (Su et al 1998) contains a constitutivepromoter (rice Act1) for driving the expression of the P5CS cDNA (p5cs). pJS112contains an ABA-inducible promoter, the AIPC (Su et al 1998), for driving the expressionof p5cs; the AIPC used in the present experiment contains four copies ofABRC1 from the barley HVA22 gene, the rice Act1 minimal promoter (180 bp), andthe HVA22 intron. In our previous work, using uidA gene as the reporter, AIPC-directedtransgene expression was shown to be induced 3- to 8-fold by ABA (Su et al1998). pJS110 was used as a control because it contains the same components aspJS112 except that the reporter gene is uidA. All three plasmids contain the bacterialphosphinothricin acetyl-transferase gene (bar) driven by the CaMV 35S promoter forselection.Transgenic approaches for generating rice . . . 427