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BRASSINAZOLE-RESISTANT 1 family proteins (BZRs) are central transcription factors that govern brassinosteroid (BR)-regulated gene expression and plant growth. However, it is unclear whether there exists a BZR-independent pathway that mediates BR signaling. In this study, we found that disruption of all BZR s in Arabidopsis generated a hextuple mutant (bzr-h) displaying vegetative growth phenotypes that were almost identical to those of the null mutant of three BR receptors, bri1brl1brl3 (bri-t). By RNA sequencing, we found that global gene expression in bzr-h was unaffected by 2 h of BR treatment. The anthers of bzr-h plants were loculeless, but a similar phenotype was not observed in bri-t , suggesting that BZRs have a BR signaling-independent regulatory role in anther development. By real-time PCR and in situ hybridization, we found that the expression of SPOROCYTELESS (SPL), which encodes a transcription factor essential for anther locule development, was barely detectable in bzr-h , suggesting that BZRs regulate locule development by affecting SPL expression. Our findings reveal that BZRs are indispensable transcription factors required for both BR signaling and anther locule development, providing new insight into the molecular mechanisms underlying the microsporogenesis in Arabidopsis. This study shows that BZR1 family transcription factors (BZRs) are indispensable for both BR signaling and anther development. BZRs regulate anther development by affecting the expression of SPL , but via a mechanism that is independent of known BR receptors. [ABSTRACT FROM AUTHOR]

Plant reproductive organs are vulnerable to heat, but regulation of heat-shock responses in inflorescence is largely uncharacterized. Here, we report that two of the SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL) transcriptional factors in Arabidopsis , SPL1 and SPL12, act redundantly in thermotolerance at the reproductive stage. The spl1-1 spl12-1 inflorescences displayed hypersensitivity to heat stress, whereas overexpression of SPL1 or SPL12 enhanced the thermotolerance in both Arabidopsis and tobacco. RNA sequencing revealed 1939 upregulated and 1479 downregulated genes in wild-type inflorescence upon heat stress, among which one-quarter (1,040) was misregulated in spl1-1 spl12-1 , indicating that SPL1 and SPL12 contribute greatly to the heat-triggered transcriptional reprogramming in inflorescence. Notably, heat stress induced a large number of abscisic acid (ABA) responsive genes, of which ∼39% were disturbed in heat induction in spl1-1 spl12-1 inflorescence. Preapplication of ABA and overexpression of SPL1 restored the inflorescence thermotolerance in spl1-1 spl12-1 and in the ABA biosynthesis mutant aba2-1 , but not in the pyl sextuple mutant defective in ABA receptors PYR1 / PYL1 / PYL2 / PYL4 / PYL5 / PYL8 . Thus, inflorescence thermotolerance conferred by SPL1 and SPL2 involves PYL-mediated ABA signaling. The molecular network consisting of SPL1 and SPL12 illustrated here shed new light on the mechanisms of plant thermotolerance at the reproductive stage. [ABSTRACT FROM AUTHOR]

During the course of their life cycles, plants undergo various morphological and physiological changes underlying juvenile-to-adult and adult-to-flowering phase transitions. To flower or not to flower is a key step of plasticity of a plant toward the start of its new life cycle. In addition to the previously revealed intrinsic genetic programs, exogenous cues, and endogenous cues, a class of small non-coding RNAs, microRNAs (miRNAs), plays a key role in plants making the decision to flower by integrating into the known flowering pathways. This review highlights the age-dependent flowering pathway with a focus on a number of timing miRNAs in determining such a key process. The contributions of other miRNAs which exist mainly outside the age pathway are also discussed. Approaches to study the flowering-determining miRNAs, their interactions, and applications are presented. [ABSTRACT FROM AUTHOR]