Strigolactone (SL) mutants display a range of phenotypes, such as increased branching, reduced stature, and a loss of SLs exuded from roots into the soil. SL biosynthesis is complex and divergent between plant species. Recently, mutants defective in specific SL biosynthesis genes have shown a loss of exuded SLs, but no obvious change in branching (tillering). This means that functional specification may exist between certain SL subtypes. It has been suggested that the LATERAL BRANCHING OXIDOREDUCTASE (LBO) enzyme acts in a subpathway of SLs that is specific for branching. Here we report that barley plants mutant in hvlbo have increased tillering, but normal production of SLs detected in roots and root exudates. This finding supports the idea that SLs have functional or tissue-specific differences and that the LBO pathway has specificity for bud outgrowth rather than exudates.

The strigolactone (SL) plant hormone pathway inhibits tiller bud outgrowth. SLs also influence plant height, grain number, and grain size, but it is unclear how these traits are connected. To separate the effects of SLs on plant architecture, grain size, and yield, we tested SL barley mutant plants in a range of conditions and utilized exogenous hormone-related treatments. SL mutants consistently showed smaller average grain mass, even when tiller number was similar to that of the wild type. However, direct hormone treatments of developing grains caused a reduction in grain size, while inhibition of the pathway had an opposite effect. A direct effect of SL in the grain is consistent with the expression of specific SL-related genes across key stages of grain development. These findings suggest that SLs have a dual action by regulating vegetative stages to indirectly promote barley grain size, while directly repressing grain size later during reproduction. This raises important implications for increasing crop yield through manipulation of the SL pathway.

Plant cells maintain a low luminal pH in the trans-Golgi-network/early endosome (TGN/EE), the organelle in which the secretory and endocytic pathways intersect. Impaired TGN/EE pH regulation translates into severe plant growth defects. The identity of the proton pump and proton/ion antiporters that regulate TGN/EE pH have been determined, but an essential component required to complete the TGN/EE membrane transport circuit remains unidentified - a pathway for cation and anion efflux. Here, we have used complementation, genetically encoded fluorescent sensors, and pharmacological treatments to demonstrate that cation chloride cotransporter (CCC1) is this missing component necessary for regulating TGN/EE pH and function. Loss of CCC1 function leads to alterations in TGN/EE-mediated processes including endocytic trafficking, exocytosis, and response to abiotic stress, consistent with the multitude of phenotypic defects observed in knockout plants. This discovery places CCC1 as a central component of plant cellular function.

Cytochrome P450 enzymes encoded by ()-like genes produce most of the structural diversity of strigolactones during the final steps of strigolactone biosynthesis. The diverse copies of in provide a resource to investigate why plants produce such a wide range of strigolactones. Here we performed in silico analyses of transcription factors and microRNAs that may regulate each rice , and compared the results with available data about expression profiles and genes co-expressed with genes. Data suggest that distinct mechanisms regulate the expression of each . Moreover, there may be novel functions for homologues, such as the regulation of flower development or responses to heavy metals. In addition, individual could be involved in specific functions, such as the regulation of seed development or wax synthesis in rice. Our analysis reveals potential new avenues of strigolactone research that may otherwise not be obvious.