Hindawi Publishing Corporation BioMed Research International Volume 2013, Article ID 256549, 9 pages http://dx.doi.org/10.1155/2013/256549 Research Article Photosystem II Photochemistry and Phycobiliprotein of the Red Algae Kappaphycus alvarezii and Their Implications for Light Adaptation Xiangyu Guan, 1 Jinfeng Wang, 2 Jianyi Zhu, 3 Chunyan Yao, 3 Jianguo Liu, 2 Song Qin, 4 and Peng Jiang 2 1 School of Ocean Sciences, China University of Geosciences, Beijing 100083, China 2 Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China 3 Department of Biology, Changshu Institute of Technology, Changshu 215500, China 4 Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai 264003, China Correspondence should be addressed to Song Qin; sqin@yic.ac.cn and Peng Jiang; jiangpengqdio@163.com Received 1 September 2013; Accepted 19 October 2013 Academic Editor: Hanzhi Lin Copyright © 2013 Xiangyu Guan et al. his is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Photosystem II photochemistry and phycobiliprotein (PBP) genes of red algae Kappaphycus alvarezii, raw material of -carrageenan used in food and pharmaceutical industries, were analyzed in this study. Minimum saturating irradiance (  ) of this algal species was less than 115 mol m −2 s −1 . Its actual PSII eiciency (yield II) increased when light intensity enhanced and decreased when light intensity reached 200 mol m −2 s −1 . Under dim light, yield II declined at irst and then increased on the fourth day. Under high light, yield II retained a stable value. hese results indicate that K. alvarezii is a low-light-adapted species but possesses regulative mechanisms in response to both excessive and deicient light. Based on the PBP gene sequences, K. alvarezii, together with other red algae, assembled faster and showed a closer relationship with LL-Prochlorococcus compared to HL-Prochlorococcus. Many amino acid loci in PBP sequences of K. alvarezii were conserved with those of LL-Prochlorococcus. However, loci conserved with HL- Prochlorococcus but divergent with LL-Prochlorococcus were also found. he diversities of PE and PC are proposed to have played some roles during the algal evolution and divergence of light adaption. 1. Introduction Kappaphycus alvarezii (Doty) Doty (Rhodophyta, Solieri- aceae) is a commercially important marine alga for its high production of polysaccharide -carrageenan, which is commonly used in food, medicine, and cosmetic industries [1, 2]. Extensive application and increasing demand make K. alvarezii widely cultivated around Southeast Asia, East Africa, and South America and promote approximately 8% growth rates annually in the carrageenan industry [3, 4]. Photosynthetic responses of K. alvarezii have frequently been detected to clarify the optimal conditions that would maximize its photosynthesis and growth. For example, the efects of temperature, salinity, and UVB radiation on dif- ferent morphotypes of K. alvarezii were evaluated under controlled conditions [5–7]. However, little is known about their physiological changes associated with light intensities, and the optimal photosynthetic available radiation levels of many locally cultivated strains remain to be determined. Photosystem (PS) II photochemical parameters measured by pulse amplitude modulation (PAM) luorometry have long been used for evaluating the photosynthetic physiology of land plants [8, 9]. Moreover, its application development can easily be found in algal research [10–12]. It should be a feasible tool for in vivo testing of the photosynthetic behaviors of K. alvarezii to diferent radiations as well as for ascertaining the best light conditions. Photosynthetic behaviors and light response of plants are largely determined and regulated by their photosynthetic units [13, 14]. Phycobilisomes (PBSs) are major photosyn- thetic units that endue K. alvarezii and other red algae, cyanobacteria, several cryptomonads, and brown algae with