Cloning two P5CS genes from bioenergy sorghum and their expression profiles under abiotic stresses and MeJA treatment. Plant Science, 2011, 652-659.

ManSu a,b, Xiao-FengLi a , Xing-YongMa a, b, Xian-JunPeng a,b , Ai-GuoZhao a,b, Li-QinCheng a, Shuang-YanChen a, Gong-SheLiu a

a R&D Laboratory of Plant Resources, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, PR China

b Graduate University of Chinese Academy of Sciences, Beijing 100049, PR China

Abstract

Sweet sorghum (Sorghum bicolor(Linn.) Moench) has promise as a bioenergy feedstock in China and other countries for its use in the production of ethanol as the result of its high fermentable sugar accumulation in stems. To boost biofuel production and extend its range, we seek to improve its stress tolerance. Proline acts as an osmolyte that accumulates when plants are subjected to abiotic stress. P5CS (Δ1-pyrroline-5-carboxylate synthetase) is a key regulatory enzyme that plays a crucial role in proline biosynthesis. We isolated two closely relatedP5CSgenes from sweet sorghum, designatedSbP5CS1(GenBank accession number: GQ377719) andSbP5CS2(GenBank accession number: GQ377720), which are located on chromosome 3 and 9 and encode 729 and 716 amino acid polypeptides, respectively. The homology between the two sweet sorghumP5CSgenes was 76%. Promoter analysis of the twoP5CSgenes revealed that both sequences not only contained the expected cis regulatory regions such as TATA and CAAT boxes, but also had many stress response elements. Expression analysis revealed thatSbP5CS1andSbP5CS2transcripts were up-regulated after treatment of 10-day-old seedlings of sweet sorghum with drought, salt (250 mM NaCl) and MeJA (10 μM). The expression levels of the bothSbP5CSgenes were significantly increased after 3-day drought stress. Under high salt treatment, peakSbP5CS1expression was detected at 4 h and 8 h forSbP5CS2in roots, while the trends of expression were nearly identical in leaves. In contrast, under drought and high salt stress, the up-regulated expression ofSbP5CS1was higher than that ofSbP5CS2. When the seedlings were exposed to MeJA, rapid transcript induction ofSbP5CS1was detected at 2 h in leaves, and theSbP5CS2expression level increase was detected at 4 h post-treatment.SbP5CS1andSbP5CS2also show different temporal and spatial expression patterns.SbP5CS2gene was ubiquitously expressed whereasSbP5CS1was mainly expressed in mature vegetative and reproductive organs. Proline concentration increased after stress application and was correlated withSbP5CSexpression. Our results suggest that theSbP5CS1andSbP5CS2are stress inducible genes but might play non-redundant roles in plant development. The two genes could have the potential to be used in improving stress tolerance of sweet sorghum and other bioenergy feedstocks.