Narrow Results

The article is about the sequencing of the rice genome, benefits of biotechnology, beyond rice breeding, financial constraint, the cooperation with private sector, public-privatization act, International Functional Genomics Working Group and the training of the scientists.

The article is about the rice biotech research at the Taiwan Agricultural Research Institute.

The photosynthetic characteristics of four transgenic rice lines overexpressing maize phosphoenolpyruvate carboxylase (PEPC; line PC), pyruvate, orthophosphate dikinase (PPDK; line PK), PEPC + PPDK (line CK), and NADP-malic enzyme (NADP-ME; line ME) were investigated using outdoor-grown plants. Relative to untransformed wild-type (WT) rice, PC transgenic rice exhibited high PEPC activity (a 25-fold increase) and enhanced activity of carbonic anhydrase (more than a twofold increase). The PC transgenic plants also showed a higher CO₂ uptake rate and carboxylation efficiency, and slightly reduced CO₂ compensation point. Furthermore, PC transgenic rice produced 22% more grains than WT plants. Labeling with ¹⁴CO₂ for 20 s showed more ¹⁴C distributed to C₄ primary photosynthate aspartate and feeding with exogenous C₄ primary products such as oxaloacetate (OAA), malate (MA), or phosphoenolpyruvate (PEP) showed an increment of photosynthetic rate in PC transgenic rice, suggesting that a limited C₄ cycle exists in leaves of transgenic rice.

Introduction of the maize PEPC gene could activate or induce activities of the key enzymes scavenging active oxygen, such as superoxide dismutase (SOD) and peroxidase (POD).

The line JAAS45 manifested higher photosynthetic rates and photochemical efficiency of PS II (F_v/F_m). The value of δ¹³C in PC transgenic rice was similar to that in untransformed rice, demonstrating that transgenic rice is still a C₃ plant.

How can we redesign C₄ rice from the limited C₄ features of photosynthesis reached currently? In future work, introduction of the PEPC gene from a CAM plant into C₄-enzyme transgenic rice could carry out higher photosynthesis day and night. Simultaneously, the enhancement of endogenous ATP in PK transgenic rice through genetic engineering would increase its operation of the C₄ cycle. Most importantly, recent advanced techniques such as laser capture microdissection enable us to study the mechanisms of cellular differentiation, for example, of bundle sheath cells. From the above suggestions, these techniques might shed light on a new green revolution in rice breeding.