Sarunyaporn Maksup. Changes of sugar alcohol content and related gene expression during early period of salt stress in Thai rice (Oryza sativa L. SPP. indica) lines . Master's Degree(Plant Science). Mahidol University. : Mahidol University, 2007.
Changes of sugar alcohol content and related gene expression during early period of salt stress in Thai rice (Oryza sativa L. SPP. indica) lines
Abstract:
Salinity is one of the major problems that limits growth and yield of Thai rice
lines. An immediate response to salt stress by alteration of sugar alcohol contents was
observed in rice within an hour in preliminary observations. The aim of this thesis
was to deeply investigate the sugar alcohol profiles and the expression level of sugar
alcohol-related genes in rice seedlings during early exposure period to salt stress. In
vitro seedlings of 11 Thai rice lines (Hawm Pae-palo, Hawm Durian, Hawm Phrae,
Hawm Thong, Hawm Tang, Hawm Jampa, Hawm Nang Nuan, Hawm Sa-dung,
Hawm, Hawm Mae-jan, and Hawm Jan) grown under a photoautotrophic condition
were subjected to different salt stress conditions over a one hour period. The sugar
alcohol profiles were monitored by HPLC technique and the expression of sugar
alcohol-related genes by RT-PCR. The well-known salt tolerant rice “Pokkali” and
the salt sensitive rice “IR29” were used as a positive and a negative control,
respectively. The Thai salt-tolerant lines (Hawm Pae-palo, Hawm Thong, Hawm Jan,
and Hawm) responded to salt stress (342 mM NaCl) differently from Pokkali and
IR29. During the hour of salt stress, the Thai salt-tolerant lines drastically increased
the levels of 6-carbon sugar alcohols (mannitol and/or sorbitol) while Pokkali
dramatically increased the levels of 4-carbon sugar alcohol (erythritol) in leaves but
IR29 did not. Thus, the salt tolerant characteristics of Thai rice may be indicated by
the rapid increase of mannitol contents and the alteration of SDH and Mtd genes
expression in leaf tissues within 1 h of salt stress. Moreover, erythritol, mannitol, or
sorbitol might transport from roots to leaves within 1 h. Then it might function as a
root-to-leaf signal transduction under salt stress. The rice lines (Hawm Pae-palo,
Hawm Thong, Hawm, and Pokkali) that spend less time in signaling showed more
tolerance to salinity stress than the lines (Hawm Jan and IR29) that spend longer time.