SUMMARY To maintain cellular homeostasis, the actions of growth-promoting hormones must be attenuated when nutrient and energy become limiting. The molecular mechanisms that coordinate hormone-dependent growth responses with nutrient availability remain poorly understood in plants [1, 2]. The Target Of Rapamycin (TOR) kinase is an evolutionarily conserved master regulator that integrates nutrient and energy signaling to regulate growth and homeostasis in both animals and plants [3–7]. Here, we show that sugar signaling through TOR controls the accumulation of the brassinosteroid (BR)-signaling transcription factor BZR1, which is essential for growth promotion by multiple hormonal and environmental signals [8–11]. Starvation, caused by shifting light-grown Arabidopsis seedlings into darkness, as well as inhibition of TOR by inducible RNAi, led to plant growth arrest and reduced expression of BR-responsive genes. The growth arrest caused by TOR inactivation was partially recovered by BR treatment and the gain-of-function mutation bzr1-1D, which causes accumulation of active forms of BZR1 [12]. Exogenous sugar promoted BZR1 accumulation and seedling growth, but such sugar effects were largely abolished by inactivation of TOR, whereas the effect of TOR inactivation on BZR1 degradation is abolished by inhibition of autophagy and by the bzr1-1D mutation. These results indicate that cellular starvation leads sequentially to TOR inactivation, autophagy, and BZR1 degradation. Such regulation of BZR1 accumulation by glucose-TOR signaling allows carbon availability to control the growth promotion hormonal programs, ensuring supply-demand balance in plant growth.

HighlightThe rice SLG gene, functioning as homomers, plays essential roles in regulating grain size and leaf angle via modulation of brassinosteroid homeostasis.

DWARF1 functions as a brassinosteroid C-24 reductase that converts 24-methylene brassinosteroids to 24-methyl brassinosteroids to regulate the endogenous level of an active brassinosteroid, castasterone, to control growth and development in Arabidopsis.

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Hipparchia autonoe (Esper, 1783) is a protected butterfly species found in Mt. Halla in South Korea. We have determined mitochondrial genome of H. autonoe collected in Mt. Halla. The circular mitogenome of H. autonoe is 15,300 bp long, which is shorter than previously sequenced mitogenome by 189 bp due to differences of tandem repeats. It includes 13 protein-coding genes, 2 ribosomal RNA genes, and 22 transfer RNAs. The base composition was AT-biased (78.9%). Nineteen single nucleotide polymorphisms and one insertion and deletion were identified between the two individuals of H. autonoe captured in Mt. Halla, presenting enough genetic diversity of H. autonoe within population.