Research Profiles
Markers for drought resistance in rice
creasing RuBisCO [indicates] the level of damage,” says Komatsu. The other 10 proteins were present at higher levels in plants that received minimal water than in control plants. Some of these proteins, such as superoxide dismutase (SOD), are involved in protecting the plant against cellular damage. Other up-regulated proteins f unction in the photosynthetic process and metabolism. Komatsu and Ali also compared the effects of 2 days of drought, osmotic,
drought and osmotic stresses. The protein levels in a drought-tolWidely known as the world’s most imerant rice cultivar called Zhonghua 8 portant crop, rice is the main dietary were compared with the levels in the staple for half of the earth’s population. Nipponbare cultivar used for the studMany research dollars are currently ies described above. The plants were directed toward studying this plant subjected to drought conditions for 2 because of its importance to world days and then were watered normalhealth and nutrition. Several transgenly for 4 days. The Nipponbare plants ic strains have been created, and the sustained more damage and grew to a genomes of two rice species have been shorter average height than the Zhongsequenced. hua 8 plants after the restoration of norAccording to Setsuko Komatsu at the mal watering. “Because actin depolyNational Institute of Agromerizing factor and proteins biological Sciences (Jainvolved in photosystem II . . . pan), however, few studies were present in high levels in have focused on determinZhonghua 8 [during normal ing global protein changes watering and drought conin rice after drought condiditions], overexpression of tions arise. This lack of data these proteins in rice might prompted Komatsu and Ghu [cause] resistance to drought lam Muhammad Ali to use stress,” says Komatsu. proteomics techniques to Actin depolymerizing facfind proteins that are differtor was up-regulated during entially regulated shortly afdrought and osmotic stress ter a drought begins. “The and in all organs of the rice genes encoding the identiplant that were studied unfied proteins can [then] be der reduced water condimanipulated for the protions. Komatsu concludes duction of drought-tolerant that this protein is an importransgenic plants,” explains tant drought stress target. Komatsu. “Actin depolymerizing facAs described in this issue tor has been implicated in of JPR (pp 396–403), Komatthe remodeling of actin filsu and Ali analyzed the proaments in plants,” she exteins in rice leaf sheaths by plains. Work by other groups 2DE after 2-week-old seedhas correlated actin depolylings were exposed to a simmerization with K+ channel Drought damage. The Nipponbare cultivar (left) grows to a shorter ulated drought. These plants regulation in the guard cells height and has more brown areas than the drought-tolerant cultivar were given 10% of the norof plants. Therefore, she says, Zhonghua 8 (right). mal amount of water, which actin could act as an osmothe control plants received. sensor. After 6 days, 35 proteins In the future, Komatsu were identified as differentially regusalt, cold, and abscisic acid (ABA) plans to focus more intently on the lated. Of these proteins, 12 showed difstresses on rice plants. Again, the levels characterization of actin depolymerferences in regulation in as soon as 2– of the same 12 proteins changed under izing factor and its relationship to 5 days after water-reduction measures drought conditions in this experiment. drought stress by producing a transwere taken. Osmotic stress resulted in the differgenic rice strain that overexpresses that To further study the early-response ential regulation of eight proteins. The protein. The ultimate goal, she says, is proteins, seedlings were exposed to levels of seven proteins were altered by to breed plants that exhibit enhanced drought conditions for only 2 days, and salt stress; the levels of six proteins were drought tolerance. Komatsu also says the 12 differentially regulated proteins affected by exposure to the cold; and that the time has come to study subcelwere identified by Edman sequencthe levels of eight proteins were altered lular localizations in rice. “It is now esing. Both the large and small chains of by ABA treatment. The only differensential that proteomics be combined RuBisCO, an enzyme involved in cartially expressed proteins shared among with subcellular fractionation to probon fixation, were down-regulated the plants treated with various stressvide insights into stress responses for during drought. “I think that the dees were a putative actin depolymerizspecific cellular compartments and orcreasing level of RuBisCO is imporing factor, light-harvesting complex ganelles, including nuclei and memtant in elucidating the mechanism of chain II, SOD, and salt-induced probranes,” she says. drought stress in rice [because] detein, which were all up-regulated under —Katie Cottingham
228 Journal of Proteome Research • Vol. 5, No. 2, 2006
