MdFRK2-mediated sugar metabolism accelerates cellulose accumulation in apple and poplar

Abstract

Background Cellulose is not only a common component in vascular plants, but also has great economic benefits for paper, wood, and industrial products. In addition, its biosynthesis is highly regulated by carbohydrate metabolism and allocation in plant. MdFRK2, which encodes a key fructokinase (FRK) in apple, showed especially high affinity to fructose and regulated carbohydrate metabolism. Results It was observed that overexpression of MdFRK2 in apple decreased sucrose (Suc) and fructose (Fru) with augmented FRK activity in stems, and caused the alterations of many phenotypic traits that include increased cellulose content and an increase in thickness of the phloem region. To further investigate the involved mechanisms, we generated FRK2-OE poplar lines OE#1, OE#4 and OE#9 and discovered (1) that overexpression of MdFRK2 resulted in the huge increased cellulose level by shifting the fructose 6-phosphate or glucose 6-phsophate towards UDPG formation, (2) a direct metabolic pathway for the biosynthesis of cellulose is that increased cleavage of Suc into UDP-glucose (UDPG) for cellulose synthesis via the increased sucrose synthase (SUSY) activity and transcript levels of PtrSUSY1, (3) that the increased FRK activity increases the sink strength overall so there is more carbohydrate available to fuel increased cambial activity and that resulted in more secondary phloem. These results demonstrated that MdFRK2 overexpression would significantly changes the photosynthetic carbon flux from sucrose and hexose to UDPG for increased cellulose synthesis. Conclusions The present data indicated that MdFRK2 overexpression in apple and poplar changes the photosynthetic carbon flux from sucrose and hexose to UDPG for stem cellulose synthesis. A strategy is proposed to increase cellulose production by regulating sugar metabolism as a whole.

Transcriptome analysis of the transition from primary to secondary growth of vertical stem in Eucalyptus grandis

“…LRR , UGT , LAC , DUF247 and TCP11 genes were found to be closely related to the transition from primary growth to secondary growth. Among them, LAC and UGT genes were closely related to lignin formation [ 32 , 66 , 67 ]. Interestingly, AtDUF247 was expressed particularly in vascular and developing tissues, which was necessary to maintain normal cell wall composition and structure by affecting the expression of other gene members in Arabidopsis [ 68 ].…”

“…CLE and SCL are associated with cellulose synthesis [ 76 , 77 ], CESA6 which closely related to primary wall also mainly expressed in primary growth stage [ 78 , 79 ]. UDP and UGT are related to hemicellulose synthesis were also explore [ 66 , 67 ]. While PttEXP1 gene was more active in the secondary growth of mature stem segments [ 80 , 81 ].…”

Low temperature reduces potato wound formation by inhibiting phenylpropanoid metabolism and fatty acid biosynthesis

“…A variety of metabolism was involved in the formation of tuber wounds, among which, sugar metabolism, phenylpropanoid metabolism, and fatty acid biosynthesis played an important role in the formation of wounds ( Schmutz et al, 1996 ; Graca and Pereira, 2000a ; Su et al., 2021 ). We found that low-temperature treatment suppressed sugar metabolism in tubers, which may inhibit the supply of energy and precursor substance during healing ( Su et al., 2021 ). StAMY23 and StBAM1 play distinct roles in starch degradation, particularly under cold conditions.…”

“…In addition, sugar serves as an energy and carbon source for lignin and suberin synthesis in plants ( Su et al., 2021 ). The evidence from published studies reveals that sucrose formed in the leaves of potato tubers during the ripening process can be transported to potato tubers and then transformed into starch for storage.…”

Hexokinase1: A glucose sensor involved in drought stress response and sugar metabolism depending on its kinase activity in strawberry

“…We still do not know whether it was related to the sugar metabolism or signaling pathway. Several sugarmetabolism-related genes, exemplified by the MdFRK2 (Su et al, 2021) and phosphoenolpyruvate carboxykinase (PEPCK) (Osorio et al, 2013), were reported to be directly linked to the sugar accumulation of plants.…”