Abstract
Triacylglycerols (TAGs), a major lipid form of energy storage, are involved in a variety of plant developmental processes. While carbon reserves mainly accumulate in seeds, significant amounts of TAG have also been observed in vegetative tissues. Notably, the accumulation of leaf TAGs is influenced by environmental stresses such as drought stress, although underlying molecular networks remain to be fully elucidated. In this study, we demonstrate that the R2R3-type MYB96 transcription factor promotes TAG biosynthesis in Arabidopsis thaliana seedlings. Core TAG biosynthetic genes were up-regulated in myb96-ox seedlings, but down-regulated in myb96-deficient seedlings. In particular, ABA stimulates TAG accumulation in the vegetative tissues, and MYB96 plays a fundamental role in this process. Considering that TAG accumulation contributes to plant tolerance to drought stress, MYB96-dependent TAG biosynthesis not only triggers plant adaptive responses but also optimizes energy metabolism to ensure plant fitness under unfavorable environmental conditions.
Highlights
Plants synthesize TAGs for carbon and energy storage [1]
Our findings indicate the biological relevance of TAG accumulation in stress adaptation and provide an insight into how TAG biosynthesis is comprehensively regulated under adverse environmental conditions
Given that MYB96 promotes expression of DGAT1 and PDAT1 in seeds [28], we supposed that MYB96 may mediate
Summary
Biosynthesis of TAG occurs in endoplasmic reticulum (ER) by a set of membrane-associated enzymes [2]. Lysophosphatidic acid at the sn-3 position is dephosphorylated by phosphatidate phosphatase, forming diacylglycerol (DAG) [5]. A third fatty acid is transferred to the sn-3 position of DAG by diacylglycerol acyltransferase (DGAT) [6]. The DGAT1 protein plays a major role in seed oil accumulation, whereas the DGAT2 enzyme is important for unusual fatty acid accumulation [8,9]. Particular emphasis has been placed on the DGAT1 protein, because it is considered the rate-limiting enzyme in Arabidopsis TAG biosynthesis [6,10,11]
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