Drought is the leading cause of agricultural yield loss among all abiotic stresses, and the link between water deficit and phloem protein contents is relatively unexplored. Here we collected phloem exudates from Solanum lycopersicum leaves during periods of drought stress and recovery. Our analysis identified 2558 proteins, the most abundant of which were previously localized to the phloem. Independent of drought, enrichment analysis of the total phloem exudate protein profiles from all samples suggests that the protein content of phloem sap is complex, and includes proteins that function in chaperone systems, branched-chain amino acid synthesis, trehalose metabolism, and RNA silencing. We observed 169 proteins whose abundance changed significantly within the phloem sap, either during drought or recovery. Proteins that became significantly more abundant during drought include members of lipid metabolism, chaperone-mediated protein folding, carboxylic acid metabolism, abscisic acid signaling, cytokinin biosynthesis, and amino acid metabolism. Conversely, proteins involved in lipid signaling, sphingolipid metabolism, cell wall organization, carbohydrate metabolism, and a mitogen-activated protein kinase are decreased during drought. Our experiment has achieved an in-depth profiling of phloem sap protein contents during drought stress and recovery that supports previous findings and provides new evidence that multiple biological processes are involved in drought adaptation.

Cassava is an important staple crop globally; its roots and leaves are directly consumed as food or undergo secondary processing in food industries or as animal feed. Inherent biological challenges in cassava affect the quality and quantity of food and feed. Although trait consolidation has been explored, the diversity in cassava food products has led to stratification of target crop characteristics. Among the traits targeted, crop improvement for food includes: yield and starch quality for different applications such as pounding, resistant starch, waxy starch, and even post-harvest deterioration. The presence of the antinutritional compound cyanide reduces the quality of food and feed, and efforts to reduce cyanide levels are continuously explored. In this Chapter, we review biological and technological research efforts in cassava geared toward improving the quality/quantity of cassava for food and feed. These efforts cut across target trait improvement efforts to new bioprocessing technologies.