In order to prevent or counteract shading, plants enact a complex set of growth and developmental adaptations when they sense a change in light quality caused by other plants in their vicinity.  This shade avoidance response (SAR) typically includes increased stem elongation at the expense of plant fitness and yield, making it an undesirable trait in an agricultural context.  Manipulating the molecular factors involved in SAR can potentially improve productivity by increasing tolerance to higher planting density.  However, most of the investigations of the molecular mechanism of SAR have been carried out in Arabidopsis thaliana, and it is presently unclear in how far results of these investigations apply to crop plants.  In this review, current data on SAR in crop plants, especially from members of the Solanaceae and Poaceae families, are integrated with data from Arabidopsis, in order to identify the most promising targets for biotechnological approaches.  Phytochromes, which detect the change in light caused by neighboring plants, and early signaling components can be targeted to increase plant productivity.  However, they control various photomorphogenic processes not necessarily related to shade avoidance.  Transcription factors involved in SAR signaling could be better targets to specifically enhance or suppress SAR.  Knowledge integration from Arabidopsis and crop plants also indicates factors that could facilitate the control of specific aspects of SAR.  Candidates are provided for the regulation of plant architecture, flowering induction and carbohydrate allocation.  Yet to-be-elucidated factors that control SAR-dependent changes in biotic resistance and cell wall composition are pointed out.  This review also includes an analysis of publicly available gene expression data for maize to augment the sparse molecular data available for this important species.

Lipoxygenases (LOXs) are a group of non-heme, iron-containing enzymes and extensively involved in plant growth and development, ripening and senescence, stress responses, biosynthesis of regulatory molecules and defense reaction. In our previous study, 18 LOXs in melon genome were screened and identified, and five 13-LOX genes (CmLOX08, CmLOX10, CmLOX12, CmLOX13 and CmLOX18) were predicted to locate in chloroplast. Phylogenetic analysis result showed that the five genes have high homology with jasmonic acid (JA) biosynthesis-related LOXs from other plants. In addition, promoter analysis revealed that motifs of the five genes participate in gene expression regulated by hormones and stresses. Therefore, we analyzed the expressions of the five genes and LOX activity in leaves of four-leaf stage seedlings of oriental melon cultivar Yumeiren under abiotic stress: wounding, cold, high temperature and hydrogen peroxide (H2O2), and signal molecule treatments: methyl jasmonate (MeJA), abscisic acid (ABA) and salicylic acid (SA). Real time qPCR revealed that wounding and H2O2 induced the expressions of all the five genes. Only CmLOX08 was induced by cold while only CmLOX13 was suppressed by high temperature. ABA induced the expressions of CmLOX10 and CmLOX12 while inhibited CmLOX13 and CmLOX18. MeJA increased the 3 genes expressions except CmLOX08 and CmLOX13, whereas SA decreased the effect, apart from CmLOX12. All the abiotic stresses and signal molecules treatments increased the LOX activity in leaves of oriental melon. In summary, the results suggest that the five genes have diverse functions in abiotic stress and hormone responses, and might participate in defense response. The data generated in this study will be helpful in subcellular localization and transgenic experiment to understand their precise roles in plant defense response.