title: Rice chalky ring formation caused by temporal reduction in starch biosynthesis during osmotic adjustment under foehn-induced dry wind.
abstract: Foehn-like extreme hot and dry wind conditions (34°C, >2.5 kPa vapor pressure deficit, and 7 m s(-1)) strongly affect grain quality in rice (Oryza sativa L.). This is a current concern because of the increasing frequency and intensity of combined heat and water-deficit stress under climate change. Foehn-induced dry wind conditions during the grain-filling stage increase ring-shaped chalkiness as a result of spatiotemporal reduction in starch accumulation in the endosperm, but kernel growth is sometimes maintained by osmotic adjustment. Here, we assess the effects of dry wind on chalky ring formation in environmentally controlled growth chambers. Our results showed that hot and dry wind conditions that lasted for >24 h dramatically increased chalky ring formation. Hot and dry wind conditions temporarily reduced panicle water potential to -0.65 MPa; however, kernel growth was maintained by osmotic adjustment at control levels with increased transport of assimilate to the growing kernels. Dynamic tracer analysis with a nano-electrospray-ionization Orbitrap mass spectrometer and quantitative polymerase chain reaction analysis revealed that starch degradation was negligible in the short-term treatment. Overall expression of starch synthesis-related genes was found to be down-regulated at moderately low water potential. Because the events observed at low water potential preceded the packing of starch granules in cells, we concluded that reduced rates of starch biosynthesis play a central role in the events of cellular metabolism that are altered at osmotic adjustment, which leads to chalky ring formation under short-term hot and dry wind conditions.
authors.affiliation: Kyushu Okinawa Agricultural Research Center, National Agriculture and Food Research Organization, Chikugo, Fukuoka, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Wada
authors.affiliation: Kyushu Okinawa Agricultural Research Center, National Agriculture and Food Research Organization, Chikugo, Fukuoka, Japan.
authors.forename: Chisato
authors.initials: C
authors.lastname: Masumoto-Kubo
authors.affiliation: Department of Biomechanical Systems, Faculty of Agriculture, Ehime University, Matsuyama, Ehime, Japan.
authors.forename: Yousef
authors.initials: Y
authors.lastname: Gholipour
authors.affiliation: Department of Biomechanical Systems, Faculty of Agriculture, Ehime University, Matsuyama, Ehime, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Nonami
authors.affiliation: Agricultural Research Center, National Agriculture and Food Research Organization, Tsukuba, Ibaraki, Japan.
authors.forename: Fukuyo
authors.initials: F
authors.lastname: Tanaka
authors.affiliation: Department of Organic Chemistry-CIHIDECAR, Faculty of Exact and Natural Sciences, University of Buenos Aires, Buenos Aires, Argentina.
authors.forename: Rosa
authors.initials: R
authors.lastname: Erra-Balsells
authors.affiliation: Kyushu Okinawa Agricultural Research Center, National Agriculture and Food Research Organization, Chikugo, Fukuoka, Japan.
authors.forename: Koichi
authors.initials: K
authors.lastname: Tsutsumi
authors.affiliation: Clean Energy Research Center, The University of Yamanashi, Kofu, Yamanashi, Japan.
authors.forename: Kenzo
authors.initials: K
authors.lastname: Hiraoka
authors.affiliation: Kyushu Okinawa Agricultural Research Center, National Agriculture and Food Research Organization, Chikugo, Fukuoka, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Morita
mesh_terms: D056625:Endosperm / Q000033:anatomy & histology / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D006358:Hot Temperature; D009929:Organ Size / Q000187:drug effects; D012275:Oryza / Q000033:anatomy & histology* / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D009995:Osmosis / Q000187:drug effects; D010788:Photosynthesis / Q000187:drug effects; D013213:Starch / Q000096:biosynthesis*; D013997:Time Factors; D014867:Water / Q000494:pharmacology; D014919:Wind
chemical_list: D014867:Water; D013213:Starch