title: Physiological changes and sHSPs genes relative transcription in relation to the acquisition of seed germination during maturation of hybrid rice seed.
abstract: BACKGROUND
  During the production of early hybrid rice seed, the seeds dehydrated slowly and retained high moisture levels when rainy weather lasted for a couple of days, and the rice seeds easily occurred pre-harvest sprouting (PHS) along with high temperature. Therefore it is necessary to harvest the seeds before the PHS occurred.
  
  
  RESULTS
  The seeds of hybrid rice (Oryza sativa L. subsp. indica) cv. Qianyou No1 that harvests from 19 to 28 days after pollination (DAP) all had high seed vigour. The seed moisture content at 10 DAP was 36.1%, and declined to 28.6% at 19 DAP; the contents of soluble sugar and total starch increased significantly with the development of seeds. The soluble protein content, the level of abscisic acid (ABA) and gibberellin (GA3 ), and ascorbate peroxidase (APX) activity continued to decrease from 10 DAP to 19 DAP. The seeds at 19 DAP had the highest peroxidase (POD) activity and lowest catalase (CAT) activity while the superoxide dismutase (SOD) activity had no significant difference among the different developing periods. The relative expressions of genes 64S Hsp18.0 and Os03g0267200 transcripts increased significantly from 10 to 19 DAP, and then decreased. However, no significant change was recorded in soluble protein, sugar and GA3 after 16 DAP, and they all significantly correlated with seed viability and vigour during the process of seed maturity.
  
  
  CONCLUSIONS
  The seeds of hybrid rice Qianyou No1 had a higher viability and vigour when harvested from 19 DAP to 28 DAP, the transcription levels of 64S Hsp18.0 and Os03g0267200 increased significantly from 10 DAP to 19 DAP and the highest value was recorded at 19 DAP. The seeds could be harvested as early as 19 DAP without negative influence on seed vigour and viability.
authors.affiliation: Seed Science Center, College of Agriculture and Biotechnology, Zhejiang University, Hangzhou, 310058, China.
authors.forename: Li-Wei
authors.initials: LW
authors.lastname: Zhu
authors.affiliation: Zhejiang Nongke Seed Industry Co., Ltd., Hangzhou, 310021, China.
authors.forename: Dong-Dong
authors.initials: DD
authors.lastname: Cao
authors.affiliation: Seed Science Center, College of Agriculture and Biotechnology, Zhejiang University, Hangzhou, 310058, China.
authors.forename: Qi-Juan
authors.initials: QJ
authors.lastname: Hu
authors.affiliation: Seed Science Center, College of Agriculture and Biotechnology, Zhejiang University, Hangzhou, 310058, China.
authors.forename: Ya-Jing
authors.initials: YJ
authors.lastname: Guan
authors.affiliation: Seed Science Center, College of Agriculture and Biotechnology, Zhejiang University, Hangzhou, 310058, China.
authors.forename: Wei-Min
authors.initials: WM
authors.lastname: Hu
authors.affiliation: Seed Science Center, College of Agriculture and Biotechnology, Zhejiang University, Hangzhou, 310058, China.
authors.forename: Aamir
authors.initials: A
authors.lastname: Nawaz
authors.affiliation: Seed Science Center, College of Agriculture and Biotechnology, Zhejiang University, Hangzhou, 310058, China.
authors.forename: Jin
authors.initials: J
authors.lastname: Hu
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000502:physiology*; D018525:Germination / Q000502:physiology*; D005875:Gibberellins / Q000378:metabolism; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D006824:Hybridization, Genetic; D012275:Oryza / Q000235:genetics* / Q000502:physiology*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D012639:Seeds / Q000235:genetics / Q000378:metabolism*
chemical_list: D005875:Gibberellins; D006360:Heat-Shock Proteins; D010940:Plant Proteins; D000040:Abscisic Acid
keywords: antioxidants; hybrid rice; sHSPs gene expression; seed vigour