ABA-INSENSITIVE 3 with or without FUSCA3 highly up-regulates lipid droplet proteins and activates oil accumulation

Abstract

ABA-INSENSITIVE 3 (ABI3) has long been known for activation of storage protein accumulation. A role of ABI3 on oil accumulation was also previously suggested based on a decrease of oil content in seeds of abi3 mutant. However, this conclusion could not exclude possibilities of indirect or pleiotropic effects, such as through mutual regulatory interactions with FUSCA3 (FUS3), an activator of oil accumulation. To identify ABI3 functions independent of the effects of related seed transcription factors, we expressed ABI3 under control of an inducible promoter in tobacco BY2 cells and Arabidopsis rosette leaves. Inducible expression of ABI3 activated oil accumulation in these non-seed cells, demonstrating a general role of ABI3 in regulation of oil biosynthesis. Further expressing ABI3 in rosette leaves of fus3 knock-out mutant still caused up to three-fold greater triacylglycerol accumulation, indicating ABI3 can activate lipid accumulation independently of FUS3. Transcriptome analysis revealed that lipid droplet protein (LDP) genes including OLEOSINs and CALEOSINs were highly up-regulated up to 1000 times by ABI3 in the absence of FUS3, while the expression of WRI1 was doubled. Taken together, our results provide genetic evidence that ABI3 activates oil accumulation with or without FUS3, most likely through up-regulating LDPs and WRI1.

Transcriptional regulation of oil biosynthesis in seed plants: Current understanding, applications, and perspectives

“…Numerous studies suggest that four transcriptional regulators, LEAFY COTYLEDON1 (LEC1), LEAFY COTYLEDON2 (LEC2), FUSCA3 (FUS3), and ABSCISIC ACID INSENSITIVE3 (ABI3), play central roles in the process of seed development and maturation ( Giraudat et al., 1992 ; Parcy et al., 1997 ; Lotan et al., 1998 ; Luerssen et al., 1998 ; Stone et al., 2001 ; Verdier and Thompson, 2008 ; Yamamoto et al., 2010 ; Pelletier et al., 2017 ; Jo et al., 2019 ; Song et al., 2021a ). Recent evidence shows that LEC1, LEC2, FUS3, and ABI3 are also involved in the transcriptional regulation of seed oil production ( Baud et al., 2007 ; Mu et al., 2008 ; Shen et al., 2010 ; Tan et al., 2011 ; Zhang et al., 2016 ; Manan et al., 2017 ; Tian et al., 2020 ; Yang et al., 2021 ). Genes encoding these regulators are expressed predominantly during seed development and have a considerable effect on seed oil accumulation.…”

“…In the fus3 mutant, induction of ABI3 triggers strong TAG production in transgenic seedlings, suggesting that ABI3 activates oil biosynthesis in a FUS3-independent manner. Further transcriptomic analysis showed that LIPID DROPLET PROTEIN ( LDP ) genes and WRI1 are activated by ABI3 in transgenic fus3 plants ( Yang et al., 2021 ).…”

Metabolomics and Transcriptomics Analyses Reveal Regulatory Networks Associated with Fatty Acid Accumulation in Pecan Kernels

“…LEC1, LEC2, FUS3, and ABI3 are master transcription factors that control seed maturation in plants. , AtLEC1 modulates the transcription of glycolysis and glycerolipid biosynthetic genes in Arabidopsis , and the overexpression of AtLEC1 activates the global transcription of FA-related genes . ABI3 and FUS3 are B3-domain transcription factors, and both genes activated oil accumulation in the vegetative tissues of tobacco and Arabidopsis . , One LEC1 (CIL1057S0098), one FUS3 (CIL0948S0064), and two ABI3 (CIL1427S0030 and CIL1495S0014) DEGs were obtained. The LEC1 , FUS3 , and ABI3 (CIL1427S0030) DEGs exhibited the highest expression levels during the second stage, whereas another ABI3 DEG (CIL1495S0014) was initially upregulated and maintained at a high transcript level until the stage of CsM.…”

“…LEC1, LEC2, FUS3, and ABI3 are master transcription factors that control seed maturation in plants. 45,46 AtLEC1 modulates the transcription of glycolysis and glycerolipid biosynthetic genes in Arabidopsis, and the overexpression of AtLEC1 activates the global transcription of FA-related genes. 45 ABI3 and FUS3 are B3-domain transcription factors, and both genes activated oil accumulation in the vegetative tissues of tobacco and Arabidopsis.…”

“…45 ABI3 and FUS3 are B3-domain transcription factors, and both genes activated oil accumulation in the vegetative tissues of tobacco and Arabidopsis. 46,47 One LEC1 (CIL1057S0098), one FUS3 (CIL0948S0064), and two ABI3 (CIL1427S0030 and CIL1495S0014) DEGs were obtained. The LEC1, FUS3, and ABI3 (CIL1427S0030) DEGs exhibited the highest expression levels during the second stage, whereas another ABI3 DEG (CIL1495S0014) was initially upregulated and maintained at a high transcript level until the stage of CsM.…”