No abstract

The miR156-targeted SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL) transcription factors play key roles in regulating plant development, but little is known about their function in abscisic acid (ABA) signaling. Here, we report that the miR156-targeted SPLs enhance ABA responses and contribute to the inhibition of pre-harvest sprouting. We find that SPL9 directly activates the expression of ABA responsive genes through binding to their promoters. SPL9 was further shown to physically interact with ABSCISIC ACID INSENSITIVE 5 (ABI5), a master transcription factor in ABA signaling, thus promoting its association with the promoters of ABA responsive genes. Furthermore, we reveal that the protein kinases SnRK2s interact with and phosphorylate SPL9, which is essential for its role in the activation of ABA responses. Together, our results disclose a SnRK2s-SPLs-ABI5 regulatory module in ABA signaling in Arabidopsis.

The domestication gene Q is largely responsible for the widespread cultivation of wheat because it confers multiple domestication traits. However, the underlying molecular mechanisms of how Q regulates these domestication traits remain unclear. In this study, we identify a Q-interacting protein TaLAX1, a basic helix-loop-helix transcription factor, through yeast two-hybrid assays. Using biochemical and genetic approaches, we explore the roles of TaLAX1 in regulating wheat domestication traits. Overexpression of TaLAX1 produces phenotypes, reminiscent of the q allele; loss-of-function Talax1 mutations confer compact spikes, largely similar to the Q-overexpression wheat lines. The two transcription factors TaLAX1 and Q disturb each other's activity to antagonistically regulate the expression of the lignin biosynthesis-related gene TaKNAT7-4D. More interestingly, a natural variation (InDel, +/À TATA), which occurs in the promoter of TaLAX1, is associated with the promoter activity difference between the D subgenome of bread wheat and its ancestor Aegilops tauschii accession T093. This study reveals that the transcription factor TaLAX1 physically interacts with Q to antagonistically regulate wheat domestication traits and a natural variation (InDel, +/À TATA) is associated with the diversification of TaLAX1 promoter activity.