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Inorganic phosphate (Pi) is a necessary macronutrient for basic biological processes. Plants modulate their root system architecture (RSA) and cellular processes to adapt to Pi deprivation albeit with a growth penalty. Excess application of Pi fertilizer, on the contrary, leads to eutrophication and has a negative environmental impact.

Effective insect pollination requires appropriate responses to internal and external environmental cues in both the plant and the pollinator.Helianthus annuus, a highly outcrossing species, is marked for its uniform eastward orientation of mature pseudanthia, or capitula. Here we investigate how this orientation affects floral microclimate and the consequent effects on plant and pollinator interactions and reproductive fitness.

A network of environmental inputs and internal signaling controls plant growth, development and organ elongation. In particular, the growth‐promoting hormone gibberellin (GA) has been shown to play a significant role in organ elongation. The use of tomato as a model organism to study elongation presents an opportunity to study the genetic control of internode‐specific elongation in a eudicot species with a sympodial growth habit and substantial internodes that can and do respond to external stimuli. To investigate internode elongation, a mutant with an elongated hypocotyl and internodes but wild‐type petioles was identified through a forward genetic screen. In addition to stem‐specific elongation, this mutant, namedtomato internode elongated ‐1(tie‐1) is more sensitive to theGAbiosynthetic inhibitor paclobutrazol and has altered levels of intermediate and bioactiveGAs compared with wild‐type plants. The mutation responsible for the internode elongation phenotype was mapped toGA2oxidase 7, a classIII GA2‐oxidase in theGAbiosynthetic pathway, through a bulked segregant analysis and bioinformatic pipeline, and confirmed by transgenic complementation. Furthermore, bacterially expressed recombinantTIEprotein was shown to have bona fideGA2‐oxidase activity. These results define a critical role for this gene in internode elongation and are significant because they further the understanding of the role ofGAbiosynthetic genes in organ‐specific elongation.

Plants respond to neighbor shade by increasing stem and petiole elongation. Shade, sensed by phytochrome photoreceptors, causes stabilization ofPHYTOCHROME INTERACTING FACTORproteins and subsequent induction ofYUCCAauxin biosynthetic genes. To investigate the role ofYUCCAgenes in phytochrome-mediated elongation, we examined auxin signaling kinetics after an end-of-day far-red (EOD-FR) light treatment, and found that an auxin responsive reporter is rapidly induced within 2 hours of far-red exposure.YUCCA2, 5, 8,and9are all induced with similar kinetics suggesting that theycould act redundantly to control shade-mediated elongation. To test this hypothesis we constructed ayucca2, 5, 8, 9quadruple mutant and found that the hypocotyl and petiole EOD-FR and shade avoidance responses are completely disrupted. This work shows thatYUCCAauxin biosynthetic genes are essential for detectable shade avoidance and thatYUCCAgenes are important for petiole shade avoidance.

Floral attraction traits can significantly affect pollinator visitation patterns, but adaptive evolution of these traits may be constrained by correlations with other traits. In some cases, molecular pathways contributing to floral attraction are well characterized, offering the opportunity to explore loci potentially underlying variation among individuals. Here, we quantify the range of variation in floralUVpatterning (i.e.UV‘bulls‐eye nectar guides) among crop and wild accessions ofBrassica rapa. We then use experimental crosses to examine the genetic architecture, candidate loci and biochemical underpinnings of this patterning as well as phenotypic manipulations to test the ecological impact. We find qualitative variation inUVpatterning between wild (commonly lackingUVpatterns) and crop (commonly exhibitingUVpatterns) accessions. Similar to the majority of crops, recombinant inbred lines (RILs) derived from an oilseed crop × WIfast‐plant^®cross exhibitUVpatterns, the size of which varies extensively among genotypes. InRILs, we further observe strong statistical‐genetic andQTLcorrelations within petal morphological traits and within measurements of petalUVpatterning; however, correlations between morphology andUVpatterning are weak or nonsignificant, suggesting thatUVpatterning is regulated and may evolve independently of overall petal size.HPLCanalyses reveal a high concentration of sinapoyl glucose inUV‐absorbing petal regions, which, in concert with physical locations ofUV‐traitQTLs, suggest a regulatory and structural gene as candidates underlying observed quantitative variation. Finally, insects prefer flowers withUVbulls‐eye patterns over those that lack patterns, validating the importance ofUVpatterning in pollen‐limited populations ofB. rapa.