RESEARCH ARTICLE Proteomic responses of rice young panicles to salinity Aliasghar Dadashi Dooki 1, 2 , Franz J. Mayer-Posner 3 , Hossein Askari 1 , Abed-ali Zaiee 2 and Ghasem Hosseini Salekdeh 1 1 Agricultural Biotechnology Research Institute of Iran, Karaj, Iran 2 Institute of Biochemistry and Biophysics, Tehran University, Tehran, Iran 3 Bruker Daltonik, Bremen, Germany Rice (Oryza sativa) is most sensitive to salinity during the reproductive stage. We employed a proteomic approach to further understand the mechanism of plant responses to salinity at an early reproductive stage. Plants were grown in culture solution and salt stress imposed at panicle initiation. After 12 days of stress, young panicles were collected from control and salt stressed plants. The Na + and K + content of panicle and several yield components changed significantly in response to short-term salt stress. The collected panicles were sorted into three different sizes (7 6 1, 11 6 1, and 15 6 1 mm) and their proteome patterns were analyzed using 2-DE in tri- plicates. The expression pattern of 13 proteins significantly changed in all panicle sizes in re- sponse to stress. MS analysis of salt responsive proteins and 16 other highly abundant proteins of panicle led to the identification of proteins involved in several salt responsive mechanisms which may increase plant adaptation to salt stress including higher constitutive expression level and up- regulation of antioxidants, up-regulation of proteins involved in translation, transcription, signal transduction, and ATP generation. To the best of our knowledge, this is the first proteome anal- ysis of plant young panicle which may enhance our understanding of plant molecular responses to salinity. Proteome referencemap of rice young panicle is available at http://www.proteome.ir. Received: January 21, 2006 Revised: August 2, 2006 Accepted: August 29, 2006 Keywords: Oryza sativa / Oxidative stress / Panicle / Reproductive stage / Rice 6498 Proteomics 2006, 6, 6498–6507 1 Introduction Rice is the main staple food for more than half of the world’s population and supplies 30–80% of the daily calories con- sumed in Asia [1]. It is also an excellent model cereal for molecular biology and genetics research, because grass ge- nomes share a large degree of synteny and rice genome is smaller than other cereals [2]. The completion of draft ge- nome sequences of rice gives breeders access to an unprece- dented number of plant genes [3–5]. Since the genome of rice is completely sequenced, a major task left is to determine the biological functions of novel genes. Proteomics has been introduced as a powerful approach to study the function and regulation of genes. During the last decade, several studies have dealt with the construction of proteomes of different rice tissues and organelles [6]. Proteomics also provides a broad view of plant responses to biotic and abiotic stresses at the protein level [7]. Salinity is a major factor limiting rice production world- wide. It causes water deficit, ion toxicity, and nutrient defi- ciency leading to molecular damage, growth and yield reduction and even plant death. Rice is generally considered to be sensitive to salinity. In rice, yield components such as panicle length, spikelet number per panicle, and grain yield were significantly reduced by salinity [8]. Salt treatment at Correspondence: Dr. Ghasem Hosseini Salekdeh, Agricultural Biotechnology Research Institute of Iran, P.O. Box 31535-1897, Karaj, Iran E-mail: h_salekdeh@abrii.ac.ir or hsalekdeh@yahoo.com Fax: +98-261-2704539 Abbreviations: CSD, cold-shock domain; DHA, dehydroascor- bate; ENR, enoyl-ACP reductase; GPB-LR, guanine nucleotide- binding protein b-subunit-like protein; GR-RBP, glycine-rich RNA-binding protein; GSH-DHAR, glutathione-dependent dehy- droascorbate reductase; NDPK, nucleoside diphosphate kinase; PMC, pollen mother cell; ROS, reactive oxygen species; TPR, tet- ratricopeptide repeat DOI 10.1002/pmic.200600367  2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.proteomics-journal.com