title: Proteomic and Glycomic Characterization of Rice Chalky Grains Produced Under Moderate and High-temperature Conditions in Field System.
abstract: BACKGROUND
  Global climate models predict an increase in global mean temperature and a higher frequency of intense heat spikes during this century. Cereals such as rice (Oryza sativa L.) are more susceptible to heat stress, mainly during the gametogenesis and flowering stages. During periods of high temperatures, grain filling often causes serious damage to the grain quality of rice and, therefore, yield losses. While the genes encoding enzymes involved in carbohydrate metabolism of chalky grains have been established, a significant knowledge gap exists in the proteomic and glycomic responses to warm temperatures in situ. Here, we studied the translucent and opaque characters of high temperature stressed chalky grains of 2009 and 2010 (ripening temperatures: 24.4 and 28.0 °C, respectively).
  
  
  RESULTS
  Appearance of chalky grains of both years showed some resemblance, and the high-temperature stress of 2010 remarkably extended the chalking of grain. Scanning electron microscopic observation showed that round-shaped starch granules with numerous small pits were loosely packed in the opaque part of the chalky grains. Proteomic analyzes of rice chalky grains revealed deregulations in the expression of multiple proteins implicated in diverse metabolic and physiological functions, such as protein synthesis, redox homeostasis, lipid metabolism, and starch biosynthesis and degradation. The glycomic profiling has shown slight differences in chain-length distributions of starches in the grains of 2009-to-2010. However, no significant changes were observed in the chain-length distributions between the translucent and opaque parts of perfect and chalky grains in both years. The glucose and soluble starch contents in opaque parts were increased by the high-temperature stress of 2010, though those in perfect grains were not different regardless of the environmental changes of 2009-to-2010.
  
  
  CONCLUSIONS
  Together with previous findings on the increased expression of α-amylases in the endosperm, these results suggested that unusual starch degradation rather than starch synthesis is involved in occurring of chalky grains of rice under the high-temperature stress during grain filling period.
authors.affiliation: Graduate School of Science and Technology, Niigata University, Niigata, 950-2181, Japan.
authors.forename: Kentaro
authors.initials: K
authors.lastname: Kaneko
authors.affiliation: Graduate School of Science and Technology, Niigata University, Niigata, 950-2181, Japan.
authors.forename: Maiko
authors.initials: M
authors.lastname: Sasaki
authors.affiliation: Graduate School of Science and Technology, Niigata University, Niigata, 950-2181, Japan.
authors.forename: Nanako
authors.initials: N
authors.lastname: Kuribayashi
authors.affiliation: Graduate School of Science and Technology, Niigata University, Niigata, 950-2181, Japan.
authors.forename: Hiromu
authors.initials: H
authors.lastname: Suzuki
authors.affiliation: Department of Applied Biological Chemistry, Niigata University, Niigata, 950-218, Japan.
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Sasuga
authors.affiliation: Department of Applied Biological Chemistry, Niigata University, Niigata, 950-218, Japan.|Present address: Niigata Crop Research Center, Niigata Agricultural Research Institute, Nagaoka, 940-0826, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Shiraya
authors.affiliation: Graduate School of Science and Technology, Niigata University, Niigata, 950-2181, Japan.
authors.forename: Takuya
authors.initials: T
authors.lastname: Inomata
authors.affiliation: Graduate School of Science and Technology, Niigata University, Niigata, 950-2181, Japan.
authors.forename: Kimiko
authors.initials: K
authors.lastname: Itoh
authors.affiliation: Graduate School of Science and Technology, Niigata University, Niigata, 950-2181, Japan.
authors.forename: Marouane
authors.initials: M
authors.lastname: Baslam
authors.affiliation: Graduate School of Science and Technology, Niigata University, Niigata, 950-2181, Japan. t.mitsui@agr.niigata-u.ac.jp.|Department of Applied Biological Chemistry, Niigata University, Niigata, 950-218, Japan. t.mitsui@agr.niigata-u.ac.jp.
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Mitsui
keywords: Amylase; Chaperones; Endosperm; Environment; Grain chalkiness; Heat shock protein; High-temperature stress; Late embryogenesis abundant (LEA) protein; Starch granule; Stress-related protein