Abstract
Cassava is an important staple crop in tropical and sub-tropical areas. As a common farming practice, cassava is usually cultivated intercropping with other crops and subjected to various degrees of shading, which causes reduced productivity. Herein, a comparative transcriptomic analysis was performed on a series of developmental cassava leaves under both full sunlight and natural shade conditions. Gene expression profiles of these two conditions exhibited similar developmental transitions, e.g. genes related to cell wall and basic cellular metabolism were highly expressed in immature leaves, genes involved in lipid metabolism and tetrapyrrole synthesis were highly expressed during the transition stages, and genes related to photosynthesis and carbohydrates metabolism were highly expressed in mature leaves. Compared with the control, shade significantly induced the expression of genes involved in light reaction of photosynthesis, light signaling and DNA synthesis/chromatin structure; however, the genes related to anthocyanins biosynthesis, heat shock, calvin cycle, glycolysis, TCA cycle, mitochondrial electron transport, and starch and sucrose metabolisms were dramatically depressed. Moreover, the shade also influenced the expression of hormone-related genes and transcriptional factors. The findings would improve our understanding of molecular mechanisms of shade response, and shed light on pathways associated with shade-avoidance syndrome for cassava improvement.
Highlights
The yield was reduced[14]
The molecular mechanism of shade avoidance is emerging in recent years; these studies were mainly conducted in model plant of Arabidopsis, while much less information is available for food crops, especially for tropical crops
It would be important to increase our understanding of the molecular mechanisms of shade response in cassava, which is directly associated with its production when intercropping with other crops and/or under cloudy weather
Summary
The yield was reduced[14]. The ultimate goal is to eliminate/minimize SAS in crops. Under shade condition with low R:FR ratio, the pool of PIFs increases, the PIFs bind promoters and regulate the expression of genes that promote the shade avoidance, including the homeodomain-Leucine zipper (HD-Zip) II family members, e.g. AtHB-2 and AtHB-4 in Arabidopsis, as well as genes that play critical roles in auxin biosynthesis, signaling and transport[17,18,19]. The molecular mechanism of shade avoidance is emerging in recent years; these studies were mainly conducted in model plant of Arabidopsis, while much less information is available for food crops, especially for tropical crops (e.g., cassava). It would be important to increase our understanding of the molecular mechanisms of shade response in cassava, which is directly associated with its production when intercropping with other crops and/or under cloudy weather. The results will provide new insights into the shade response of cassava, and improve our understanding of mechanisms that trigger SAS and help cassava improvement of the yield
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