*11.2. Genome Editing to Target the Metabolic Processes Consuming Carbon*

The genetic improvement of crops by using genome editing approaches like knockout, replacement base editing, and regulation of expression of desirable/undesirable genes can effectively target the metabolic processes that lead to futile carbon loss in crops. The few pathways that can be replaced, relocated, or rescheduled through this approach have been discussed (Figure 4).

#### 11.2.1. Substitution of the Lignin Biosynthesis Pathway

The lignin biosynthesis pathway involving phenylalanine ammonia lyase (PAL) can be overridden by substitution with tyrosine ammonia lyase (TAL) as it provides a gain due to the formation of two NADPH per *p*-coumarate [121] and can potentially decrease growth respiration [32].

**Figure 4.** Respiratory carbon loss in plants and strategies to enhance yield under high temperature.

#### 11.2.2. Suppression of Futile Cycles

A substantial proportion of the ATP generated during respiration is consumed by certain pathways that can be called 'futile' cycles. For example, the simultaneous synthesis and degradation of starch in leaves during the day [122], the simultaneous synthesis and degradation of sucrose [123], and cycling between fructose 6-phosphate and fructose 1,6 bisphosphate [124] are futile cycles. The suppression of these futile cycles will decrease the respiratory costs without exerting collateral damage on the metabolic machinery [32].
