Análise fisiológica, transcricional e do perfil metabólico de diferentes estágios de desenvolvimento da folha +1 de cana de açúcar sob diferentes concentrações de nitrogênio (N)

Author(s)

Denis Bassi

• Document type: Doctoral Thesis
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Faculdade de Engenharia de Alimentos
• Defense date: 2018-07-12

Examining board members

Marcelo Menossi; Monalisa Sampaio Carneiro; Renato Vicentini; Ladaslav Sodek; Marcelo de Almeida Silva

• Advisor: Marcelo Menossi; Lucia Mattiello

Abstract

Sugarcane is considered the most important crop in the Brazilian bioenergetic sector and the investments to obtain cultivars with higher productivity are constant. A potential strategy to leverage sugarcane yields is the increase of photosynthesis, the main energetic mechanism in plants. Besides several environmental factors, some nutrients, such as the nitrogen (N), present an important role in photosynthesis. However, the complex relation between leaf development, photosynthesis and N is poorly understood in sugarcane. Therefore, this study aimed to verify the differences in physiological, transcriptional and metabolic profile in different developmental stages along sugarcane leaf blade and to explore the effect of N in the photosynthesis establishment and other processes related to growth and leaf development. To achieve these goals, physiological, transcriptional and metabolic analyses were realized in four different leaf segments (base zero, base, middle and tip) along the leaf +1 in two distinct experiments. In the first experiment, plants were grown without differential N supply, while in the second one plants of two contrasting genotypes, one responsive (R) and other nonresponsive (NR) to N supply were grown under low and high N conditions. The four leaf segments presented physiological differences, which indicated a differential photosynthetic capacity among them. Furthermore, transcriptional analysis revealed the presence of a development gradient along sugarcane leaf, as observed in other grass species, such as maize. However, the transcriptional profile of each segment showed significant differences when compared to segments of the maize leaf, indicating a distinct transcriptional regulation between these two species. The N and genotype responsiveness determined the senescence degree, the carboxylation process mediated by PEPcase and the differential accumulation of soluble sugars along the sugarcane leaf. A higher concentration of metabolites related to photosynthesis was observed in almost all leaf segments of the R genotype compared to the NR genotype under high N conditions. The levels of malate and pyruvate were higher in the median region of leaf in the R genotype in comparison to NR genotype under high N conditions. Furthermore, the level of ribose was higher in almost all leaf segments of R genotype when cultivated under high N. This suggests that N and the genotype responsiveness influenced photosynthesis. Curiously, the NR genotype showed the highest number of differentially expressed transcripts in response to N supply. On the other hand, the number of transcripts with high expression level was greater in the R genotype. In addition, we evidenced that the transcriptional regulation of diverse pathways related to growth and leaf development was modulated by N and varied according to the responsiveness of the genotypes and the leaf segment. The results presented provided a better understanding on the photosynthesis establishment along the sugarcane leaf and the molecular basis involved with N effect on leaf development and photosynthesis (AU)

• FAPESP's process: 14/03562-2 - Physiological, transcriptional and metabolites analysis of different developmental stages of sugarcane leaf +1
• Grantee: Denis Bassi
• Support Opportunities: Scholarships in Brazil - Doctorate