Amylopectin Chain Length Dynamics and Activity Signatures of Key Carbon Metabolic Enzymes Highlight Early Maturation as Culprit for Yield Reduction of Barley Endosperm Starch after Heat Stress

Abstract

Abiotic environmental stresses have a negative impact on the yield and quality of crops. Understanding these stresses is an essential enabler for mitigating breeding strategies and it becomes more important as the frequency of extreme weather conditions increases due to climate change. This study analyses the response of barley (Hordeum vulgare L.) to a heat wave during grain filling in three distinct stages: the heat wave itself, the return to a normal temperature regime, and the process of maturation and desiccation. The properties and structure of the starch produced were followed throughout the maturational stages. Furthermore, the key enzymes involved in the carbohydrate supply to the grain were monitored. We observed differences in starch structure with well-separated effects because of heat stress and during senescence. Heat stress produced marked effects on sucrolytic enzymes in source and sink tissues. Early cessation of plant development as an indirect consequence of the heat wave was identified as the major contributor to final yield loss from the stress, highlighting the importance for functional stay-green traits for the development of heat-resistant cereals.

Photoprotection and optimization of sucrose usage contribute to faster recovery of photosynthesis after water deficit at high temperatures in wheat

“…Higher activity of vacINV has been reported in maize leaves under water deprivation conditions (Pelleschi et al ., 1997; Trouverie et al ., 2003), although in sugarcane (Wang et al ., 2017), cytINV was also shown to play a more prominent role than vacINV under abiotic stress. In barley, activities of both vacINV and cytINV were repressed after a heat stress episode (Cuesta‐Seijo et al ., 2019). In tomato, ectopic expression of cell wall invertases resulted in drought tolerance that was accompanied by also changes in cytINV and vacINV (Albacete et al ., 2015).…”

A Review of Starch Biosynthesis in Relation to the Building Block-Backbone Model

“…Indeed, one proposed function for SSIII in amylopectin synthesis in other structural models is the provision of the long, cluster-interconnecting chains of the amylopectin backbone [ 198 ]. All of the aforementioned α-glucan chain groups are found in abundance in plant amylopectins and, together with analysis of various SS mutants (see [ 48 , 133 , 199 ]), suggest a crucial role for SSI, SSII and SSIII in building the building blocks/blocklets and backbone ( Table 1 ). In addition, the backbone may be supported by the super-long chains formed by GBSS [ 28 , 117 ].…”

Starch morphological, structural, pasting, and thermal properties of waxy maize under different heat stress durations at grain formation stage

“…The percentage of B3 chain gradually increased with extended HS durations in both hybrids (Table S2). A study on barley also showed that the frequency of A chain decreases when plants suffer from HS during the grain filling stage (Cuesta‐Seijo et al, 2019). A study on rice observed that DP 6–15 decrease and DP > 18 increase under HS (Kato et al, 2019).…”

“…The substrate transferred to existing starch granules and enlarged them because HS restricted the formation of starch granules; this phenomenon also demonstrated that starch granules are loosely packed in the endosperm (Lo et al, 2016). A study on barley demonstrated that the proportion of small B‐granules decreases but that of large A‐granules increases by HS and the restriction of B‐granule initiation by precocious senescence (Cuesta‐Seijo et al, 2019). A‐type starch granules in wheat increased in number and decreased in size, while B‐type starch granules decreased in both number and size (Hurkman & Wood, 2011).…”

“…The proportion of small B-granule decreased and that of large B-granule increased, while A granules were unaffected by HS in barley starch. In addition, the decreased abundance of degree of polymerization (DP) 7-11 and increased abundance DP 20-37 resulted in high gelatinization temperatures (Cuesta-Seijo et al, 2019). The normal maize starch granule size decreased and gelatinization temperatures increased while branch-chain fractions were different between two inbred strains in response to HS (Lu et al, 1996).…”