Regulation of fruit and seed response to heat and drought by sugars as nutrients and signals

Abstract

A large body of evidence shows that sugars function both as nutrients and signals to regulate fruit and seed set under normal and stress conditions including heat and drought. Inadequate sucrose import to, and its degradation within, reproductive organs cause fruit and seed abortion under heat and drought. As nutrients, sucrose-derived hexoses provide carbon skeletons and energy for growth and development of fruits and seeds. Sugar metabolism can also alleviate the impact of stress on fruit and seed through facilitating biosynthesis of heat shock proteins (Hsps) and non-enzymic antioxidants (e.g., glutathione, ascorbic acid), which collectively maintain the integrity of membranes and prevent programmed cell death (PCD) through protecting proteins and scavenging reactive oxygen species (ROS). In parallel, sugars (sucrose, glucose, and fructose), also exert signaling roles through cross-talk with hormone and ROS signaling pathways and by mediating cell division and PCD. At the same time, emerging data indicate that sugar-derived signaling systems, including trehalose-6 phosphate (T6P), sucrose non-fermenting related kinase-1 (SnRK), and the target of rapamycin (TOR) kinase complex also play important roles in regulating plant development through modulating nutrient and energy signaling and metabolic processes, especially under abiotic stresses where sugar availability is low. This review aims to evaluate recent progress of research on abiotic stress responses of reproductive organs focusing on roles of sugar metabolism and signaling and addressing the possible biochemical and molecular mechanism by which sugars regulate fruit and seed set under heat and drought.

Cell Wall Invertase Promotes Fruit Set under Heat Stress by Suppressing ROS-Independent Cell Death

“…These include the activities of three key antioxidant enzymes and the H 2 O 2 content (Sunkar et al, 2003(Sunkar et al, , 2006. In plants, enzymatic removal of ROS is mainly executed through the activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), and catalase (CAT; Smirnoff, 1993), and their activities are often induced by severe heat stress (Liu et al, 2013). Surprisingly, LMHS had no effect on the activities of all three enzymes in either wild-type or transgenic 2-dbp ovaries (Fig.…”

“…6, A-C 2 ), and the hydroxyl radical (OH 2 ). Among them, H 2 O 2 is thought to be relatively stable and abundant (Bienert et al, 2007) and thus the most studied ROS species (Liu et al, 2013). LMHS had no significant effect on H 2 O 2 content in wild-type 2-dbp ovaries and 2-dap fruits, nor in 2-dap transgenic fruits ( Fig.…”

“…Therefore, we measured malondialdehyde (MDA), which is the end-product of lipid peroxidation caused by ROS and hence is an excellent marker for overall oxidative stress and damage (Sunkar et al, 2003;Liu et al, 2013). Again, no difference was observed in the MDA content of 2-dbp ovaries or 2-dap fruits between wild-type and transgenic plants under either control or LMHS conditions, and LMHS did not elicit an increase of MDA content in these organs (Fig.…”

“…In broad terms, fruit abortion under heat stress could result from the activation of PCD and the repression of cell division and expansion Liu et al, 2013). To test whether LMHS induced PCD, we conducted terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay, which detects the cleavage of nuclear DNA, a hallmark of PCD or apoptosis (Wang and Ruan, 2016).…”

Effects of phosphorus application on photosynthetic carbon and nitrogen metabolism, water use efficiency and growth of dwarf bamboo ( Fargesia rufa ) subjected to water deficit

“…These situations might not only provide more carbon and energy for water-stressed dwarf bamboo to avoid carbon starvation and maintain RGR (Table 1), but also alleviate the damage of water stress to plants through facilitating biosynthesis of heat shock proteins (Hsps) and non-enzymic antioxidants (e.g. glutathione and ascorbic acid) (Liu et al, 2013). In parallel, sucrose metabolites (e.g.…”