Light, water and appropriate temperature are basic requirements for plant growth. The prospect of global climate changes impacting light, temperature and precipitation patterns have made plant environment-interaction an important topic in plant science worldwide.  The Institute of Plant and Microbial Biology (IPMB) has several research groups focused on plant response to changing environments with the goal of understanding how changing environments affect plant growth.  In the present studies, Dr. Shih-Long Tu reported that a new enzyme named phycourobilin synthase (PUBS) can synthesize an alternative chromophore (a compound that absorbs light) to regulate phytochrome (a photoreceptor which binds the chromophore to sense light) activity.  The group of Dr. Paul Verslues reported variation in levels of proline, a stress-protective compound, and production of a non-functional RNA encoding the proline synthesis enzyme P5CS1 that are associated with adaptation to different environments.

　　Light is the most important energy source for photosynthetic organisms. Phytochromes are the main photoreceptors that detect light and mediate changes in plant growth to match light conditions. Phytochromes require a chromophore cofactor to fully function.  In most plants, phytochromobilin synthase (HY2) is a key enzyme producing the chromophore for phytochromes.  However in the moss Physcomitrella patens, Dr. Tu’s laboratory identified a new second enzyme they named PUBS that can synthesize an alternative chromophore to regulate phytochrome activity. PUBS can only be found in green algae, mosses, and lycophytes, suggesting that this enzyme was important evolutionarily for green plants to adapt to light-rich environments. Dr. Tu’s team further identified phytochrome-regulated genes in Physcomitrella.  These results reveal that moss phytochromes efficiently re-program gene expression for phototrophic growth in the light. This approach allows, for the first time, a global view of phytochrome-mediated gene regulation in nonvascular plants. These new findings can be applied to agriculture, to modulate crop growth and development using light.

　　The laboratory of Dr. Paul Verslues is interested in plant responses to limited water supply during drought.  Many plants accumulate large quantities of proline during drought; however, the adaptive value of proline has remained unclear. The model plant Arabidopsis thaliana is distributed across a wide geographic and climate range and differences between Arabidopsis types can be used to discover factors, such as proline, needed for adaptation to different environments. The Verslues laboratory, along with collaborators at the University of Texas found that different types of Arabidopsis varied ten-fold in drought-responsive proline accumulation.  Some of this variation was accounted for by high levels of a non-functional RNA produced by the gene encoding the proline synthesis enzyme ?1-pyrroline-5-carboxylate synthetase1 (P5CS1).   Arabidopsis types having high levels of the non-functional P5CS1 RNA shared the same set of genetic changes that promoted alternative RNA splicing of P5CS1.  These data demonstrated a novel source of RNA splicing variation in plants and correlation of P5CS1 variation with climate data indicated a role of P5CS1 and proline synthesis in adaptation to environments differing in water availability and temperature.   The results have implications in drought-adaptation and in how proline metabolism may be best targeted in biotechnology efforts to improve drought tolerance of crop plants. 

　　The study of Dr. Tu and colleagues was published on May 7, 2012. It is entitled: “Distinct phytochrome actions in nonvascular plants revealed by targeted inactivation of phytobilin biosynthesis” and can be found at:
http://www.pnas.org/content/early/2012/05/02/1201744109.abstract
     The full list of authors is: Yu-Rong Chen, Yi-shin Su, and Shih-Long Tu.

The article of Dr. Verslues and coworkers was published on May 21, 2012. It is entitled: “Intron-mediated alternative splicing of Arabidopsis P5CS1 and its association with natural variation in proline and climate adaptation” and can be found at:
http://www.pnas.org/content/early/2012/05/17/1203433109.abstract

　　The full list of authors is: Ravi Kesari, Joji Grace Villamor, Ying-Jiun C. Chen, Tzu-Wen Liu, Wendar Lin and Paul E. Verslues of the Institute of Plant and Microbial Biology, Academia Sinica; and Jesse R. Lasky, David L. Des Marais and Thomas E. Juenger of the University of Texas-Austin.