title: Identification and Characterization of Differentially Expressed Genes in Inferior and Superior Spikelets of Rice Cultivars with Contrasting Panicle-Compactness and Grain-Filling Properties.
abstract: Breeding programs for increasing spikelet number in rice have resulted in compactness of the panicle, accompanied by poor grain filling in inferior spikelets. Although the inefficient utilization of assimilate has been indicated as responsible for this poor grain filling, the underlying cause remains elusive. The current study utilized the suppression subtractive hybridization technique to identify 57 and 79 genes that overexpressed in the superior and inferior spikelets (with respect to each other), respectively, of the compact-panicle rice cultivar Mahalaxmi. Functional categorization of these differentially expressed genes revealed a marked metabolic difference between the spikelets according to their spatial location on the panicle. The expression of genes encoding seed storage proteins was dominant in inferior spikelets, whereas genes encoding regulatory proteins, such as serine-threonine kinase, zinc finger protein and E3 ligase, were highly expressed in superior spikelets. The expression patterns of these genes in the inferior and superior spikelets of Mahalaxmi were similar to those observed in another compact-panicle cultivar, OR-1918, but differed from those obtained in two lax-panicle cultivars, Upahar and Lalat. The results first suggest that the regulatory proteins abundantly expressed in the superior spikelets of compact-panicle cultivars and in both the superior and inferior spikelets of lax-panicle cultivars but poorly expressed in the inferior spikelets of compact-panicle cultivars promote grain filling. Second, the high expression of seed-storage proteins observed in the inferior spikelets of compact-panicle cultivars appears to inhibit the grain filling process. Third, the low expression of enzymes of the Krebs cycle in inferior spikelets compared with superior spikelets of compact-panicle cultivars is bound to lead to poor ATP generation in the former and consequently limit starch biosynthesis, an ATP-consuming process, resulting in poor grain filling.
authors.affiliation: Environmental Biotechnology Laboratory, Institute of Life Sciences, Bhubaneswar, Odisha, India.
authors.forename: Sudhanshu
authors.initials: S
authors.lastname: Sekhar
authors.affiliation: Environmental Biotechnology Laboratory, Institute of Life Sciences, Bhubaneswar, Odisha, India.
authors.forename: Sachin Ashruba
authors.initials: SA
authors.lastname: Gharat
authors.affiliation: Environmental Biotechnology Laboratory, Institute of Life Sciences, Bhubaneswar, Odisha, India.
authors.forename: Binay Bhushan
authors.initials: BB
authors.lastname: Panda
authors.affiliation: Environmental Biotechnology Laboratory, Institute of Life Sciences, Bhubaneswar, Odisha, India.
authors.forename: Trupti
authors.initials: T
authors.lastname: Mohaptra
authors.affiliation: Environmental Biotechnology Laboratory, Institute of Life Sciences, Bhubaneswar, Odisha, India.
authors.forename: Kaushik
authors.initials: K
authors.lastname: Das
authors.affiliation: School of Life Sciences, Sambalpur University, Jyoti Vihar, Sambalpur, Odisha, India.
authors.forename: Ekamber
authors.initials: E
authors.lastname: Kariali
authors.affiliation: School of Life Sciences, Sambalpur University, Jyoti Vihar, Sambalpur, Odisha, India.
authors.forename: Pravat Kumar
authors.initials: PK
authors.lastname: Mohapatra
authors.affiliation: Environmental Biotechnology Laboratory, Institute of Life Sciences, Bhubaneswar, Odisha, India.
authors.forename: Birendra Prasad
authors.initials: BP
authors.lastname: Shaw
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D002952:Citric Acid Cycle / Q000235:genetics; D018076:DNA, Complementary / Q000235:genetics; D018744:DNA, Plant / Q000235:genetics; D002523:Edible Grain / Q000235:genetics / Q000378:metabolism; D020224:Expressed Sequence Tags; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D012275:Oryza / Q000235:genetics* / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D018749:RNA, Plant / Q000235:genetics; D055314:Seed Storage Proteins / Q000235:genetics / Q000378:metabolism; D066251:Subtractive Hybridization Techniques; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D018076:DNA, Complementary; D018744:DNA, Plant; D010940:Plant Proteins; D018749:RNA, Plant; D055314:Seed Storage Proteins; D014157:Transcription Factors; D000255:Adenosine Triphosphate