Local inhibition of nitrogen fixation and nodule metabolism in drought-stressed soybean

Abstract

Drought stress is a major factor limiting symbiotic nitrogen fixation (NF) in soybean crop production. However, the regulatory mechanisms involved in this inhibition are still controversial. Soybean plants were symbiotically grown in a split-root system (SRS), which allowed for half of the root system to be irrigated at field capacity while the other half remained water deprived. NF declined in the water-deprived root system while nitrogenase activity was maintained at control values in the well-watered half. Concomitantly, amino acids and ureides accumulated in the water-deprived belowground organs regardless of transpiration rates. Ureide accumulation was found to be related to the decline in their degradation activities rather than increased biosynthesis. Finally, proteomic analysis suggests that plant carbon metabolism, protein synthesis, amino acid metabolism, and cell growth are among the processes most altered in soybean nodules under drought stress. Results presented here support the hypothesis of a local regulation of NF taking place in soybean and downplay the role of ureides in the inhibition of NF.

Rendimento de grãos de soja em função de sistemas de plantio e irrigação por superfície em Planossolos

“…De acordo com Ferrari et al (2015), o estresse causado por deficit de água leva à ocorrência de plantas de soja pouco desenvolvidas, com pequena estatura e área foliar reduzida, pois uma das alterações provocadas pelo estresse hídrico é a redução do potencial hídrico foliar, que causa o fechamento estomático e, consequentemente, a diminuição das trocas gasosas e a inibição de vários processos bioquímicos e fisiológicos, como a fotossíntese, respiração, absorção de íons, metabolismo dos nutrientes, entre outros. Além disso, a irrigação incrementou a massa de matéria seca de nódulos (Tabela 2), pois a nodulação é influenciada pelo conteúdo de água no solo (Siczek & Lipiec, 2011), e a fixação biológica de N é um processo metabólico muito sensível ao deficit de água em plantas de soja (Gil-Quintana et al, 2013;King et al, 2014).…”

Mitigating dry season food insecurity in the subtropics by prospecting drought-tolerant, nitrogen-fixing weeds

“…Intra-species variation in biological nitrogen fixation has been observed throughout the legume family [30,87] including within Glycine max (soybean) [88], Lablab purpureus [89], Vicia faba (faba bean) [90,91], Trifolium alexandrinum (bersem clover) [36,[92][93][94], Phaseolus vulgaris (common bean) [95,96], Pisum sativum (green pea) [97], V. unguiculata (cowpea) [98], and Vigna aconitifolia (mothbean) [93]. Optimizing biological nitrogen fixation involves the selection of not only the best legume genotype but also selecting the most optimal legume and rhizobia combination [30].…”

Nuclear Proteomics Reveals the Role of Protein Synthesis and Chromatin Structure in Root Tip of Soybean during the Initial Stage of Flooding Stress

“…In soybean, the suppression of protein synthesis was previously reported in root including hypocotyl by flooding stress 42,43 . Furthermore, drought stress also led to suppression of protein synthesis in root tip 44,45 . In addition, the proteomic analysis of endoplasmic reticulum proteins of soybean root tip also indicated that protein synthesis was affected by flooding stress 8 .…”