Examination of the usability of leaf chlorophyll content and gene expression analyses as nitrogen status biomarkers in Sorghum bicolor

Abstract

Sorghum [Sorghum bicolor (L.) Moench] has been receiving attention as a feedstock for biomass energy. Since nitrogen (N) significantly affects the plant biomass production, diagnosing the N status of sorghum during its growth would be significant. Therefore, in this study, we analyzed the changes in several physiological parameters of sorghum in response to N limitation, with the aim of identifying candidates of N status biomarkers in this species. Parameters responding early and sensitively to N deficiency were searched in hydroponically cultured seedlings, and their applicability to field conditions was examined. We found that the leaf chlorophyll content measured as a soil-plant analysis development (SPAD) value was promising as a candidate N status biomarker, as it showed responses consistent with N regimes in field conditions in multiple genotypes. A gene expression analysis was capable of detecting N deficiency sensitively at an early stage, although its application to practical situations requires further investigation to identify a suitable sets of marker genes.

Keywords:

• chlorophyll content
• gene expression analysis
• nitrogen
• nutrition diagnosis
• Sorghum bicolor
• SPAD value

Acknowledgments

This work was supported in part by the JST-JICA SATREPS project “Producing biomass energy and material through revegetation of alang-alang (Imperata cylindrica) fields.” We thank EARTHNOTE Co. Ltd. for providing sorghum seeds, Mr. Takuya Iguchi for providing field-grown sorghum samples, Dr. Yu Tanaka in Graduate School of Agriculture, Kyoto University for the use of their spectrometer, Ms. Saori Kawamura, Ms Sayaka Shinpo and Dr. Hideyuki Suzuki for the RNA sequencing analysis, and Drs. Kumiko Ochiai and Toru Matoh for their discussion and technical guidance of analyses. R.R.R. also acknowledges the Honjo International Scholarship Foundation for supporting his study in Kyoto University.

Conflicts of interest

No potential conflict of interest was reported by the authors.