Shade stress decreases stem strength of soybean through restraining lignin biosynthesis

Abstract

Lodging is the most important constraint for soybean growth at seedling stage in maize-soybean relay strip intercropping system. In the field experiments, three soybean cultivars Nandou 032-4 (shade susceptible cultivar; B1), Jiuyuehuang (moderately shade tolerant cultivar; B2), and Nandou 12 (shade tolerant cultivar; B3) were used to evaluate the relationship between stem stress and lignin metabolism in the stem of soybean. Results showed that the intercropped soybean was in variable light condition throughout the day time and co-growth stage with maize. The xylem area and cross section ratio played a main role to form the stem stress. The B3 both in intercropping and monocropping expressed a high stem stress with higher xylem area, lignin content, and activity of enzymes (phenylalanine ammonia-lyase (PAL), 4-coumarate: CoA ligase (4CL), cinnamyl alcohol dehydrogenase (CAD), peroxidase (POD)) than those of B1 and B2. Among the soybean cultivars and planting pattern, lignin content was positively correlated with stem stress. However, a negative correlation was found between lignin content and actual rate of lodging. In conclusion, the shade tolerant soybean cultivar had larger xylem area, higher lignin content and activities of CAD, 4CL, PAL, and POD than other soybean cultivars in intercropping. The lodging in maize-soybean intercropping can be minimized by planting shade tolerant and lodging resistant cultivar of soybean. The lignin content in stem could be a useful indicator for the evaluation of lodging resistance of soybean in intercropping and activities of enzymes were the key factors that influence the lignin biosynthesis.

Slight Shading Stress at Seedling Stage Does not Reduce Lignin Biosynthesis or Affect Lodging Resistance of Soybean Stems

“…The results of correlation analysis showed that lodging resistance index was significantly positively correlated with breaking strength, which was confirmed by calculating lodging resistance index. Previous studies showed that severe shading can affect some enzymes related to lignin biosynthesis, such as 4CL, CAD and PAL, as well as the expression level of their biosynthetic genes, so as to reduce the biosynthesis of lignin and affect lodging resistance [5,37]. Correlation analysis also showed that the key enzymes of lignin biosynthesis (PAL, POD, 4CL) were significantly correlated with lignin content, xylem proportion and lodging resistance.…”

Molecular signatures of local adaptation to light in Norway spruce

“…This phenomenon can be attributed due to the variation in the SNPs in the respective genes observed in this study that follows a latitudinal cline across Sweden. Although shade stress decreases lignin leading to weak stems in many of the plant species (Wang et al 2012 ; Wu et al 2017 ; Hussain et al 2019 ; Liu et al 2019b ), the northern Norway spruce populations appear to have adapted to SHADE (or low R:FR ratio) or higher requirement of FR to maintain the growth and other regular plant processes (Clapham et al 1998 , 2002 ; Ranade and García-Gil 2013 ), which may correspond to the observed up-regulation of cell wall-related genes. It is worth mentioning that none of the populations deviated from Hardy Weinberg Equilibrium (HWE) in case of MYB3 , which suggests that the particular genetic variation in MYB3 gene (T132R) will remain constant (i.e., not evolving) in the entire population from one generation to the next in absence of disturbing forces.…”

Molecular signatures of local adaptation to light in Norway Spruce: role of lignin mediated immunity

“…This phenomenon can be attributed due to the variation in the SNPs in the respective genes observed in this study that follows a latitudinal cline across Sweden. Although shade stress decreases lignin leading to weak stem in many of the plant species (Wang et al , 2012, Wu et al , 2017, Hussain et al , 2019, Liu et al , 2019b), the northern spruce populations appear to have adapted to SHADE or low R:FR ratio or in other words higher requirement of FR to maintain the growth and other regular plant processes (Clapham et al , 1998, Clapham et al , 2002, Ranade and García-Gil, 2013), which may correspond to the observed up-regulation of cell wall related genes. It is worth mentioning that none of the ecotypes deviated from HWE in case of MYB3 , which suggests that the particular genetic variation in MYB3 gene (T132R) will remain constant (i.e., not evolving) in entire population from one generation to the next in the absence of selecting forces.…”