Overexpression of CO₂-responsive CCT protein, a key regulator of starch synthesis strikingly increases the glucose yield from rice straw for bioethanol production

Figures & data

Figure 1. Soluble sugar contents and pretreatment residue in hydrolyzate of rice straw.

Notes: Contents of glucose (A) and xylose (B), and weight of acid-insoluble residue (C) in hydrolyzate after dilute acid pretreatment of rice straw are shown. Data represent mean ± SD of five biological replicates. Asterisks indicate significant differences between non-transgenic rice and CRCT transgenic lines using the Student’s t test (*p < .05, **p < .01). NT, non-transgenic rice; OX1 and OX2, CRCT overexpression lines; RNAi, CRCT knockdown line.

Table 1. Composition of constituents in rice straw of CRCT transgenic lines.

Plant	Glucan (%)	Starch (%)	Cellulose (%)	Hemicellulose (%)	Acid-insoluble lignin (%)	Acid-soluble lignin (%)	Total (%)
NT	35.2 ± 1.5	3.4 ± .4	31.8 ± 1.5	12.3 ± .4	19.9 ± .2	17.3 ± .5	84.6 ± 1.6
OX1	40.1 ± 1.9^**	6.8 ± 1.2^**	33.4 ± 1.1	10.2 ± .9^**	15.7 ± 1.7^**	17.2 ± .4	83.3 ± 2.4
OX2	46.2 ± 4.3^**	7.3 ± .8^**	38.9 ± 4.4^*	10.7 ± .9^*	13.3 ± .8^**	17.4 ± .3	87.6 ± 2.5
RNAi	30.8 ± 2.4^*	1.2 ± .3^**	29.6 ± 2.6	14.6 ± 1.3^**	24.0 ± 1.9^*	16.8 ± .2	86.2 ± 2.8

Notes: Glucan indicates the sum of starch content and cellulose content. Total indicates the sum of all constituent contents. Data represent mean ± SD of five biological replicates. The representation of statistical significance and plants are the same as in Figure 1.

Figure 2. Fermentation inhibitor contents in hydrolyzate of rice straw.

Notes: Contents of furfural (A), 5-HMF (B), acetic acid (C) and formic acid (D) in hydrolyzate after dilute acid pretreatment of rice straw are shown. Data represent mean ± SD of five biological replicates. The representation of statistical significance and plants are the same as in Figure 1.

Figure 3. Saccharification efficiency of acid-insoluble residue.

Notes: Data represent mean ± SD of five biological replicates. The representation of statistical significance and plants are the same as in Figure 1.

Table 2. Composition of acid-insoluble residue after dilute acid pretreatment.

Plant	Cellulose (%)	Hemicellulose (%)	Acid-insoluble lignin (%)	Acid-soluble lignin (%)	Total (%)
NT	52.5 ± 1.8	1.6 ± .4	27.8 ± .3	7.2 ± .4	89.0 ± 1.7
OX1	51.2 ± 2.5	1.1 ± .4	29.2 ± 1.1	7.3 ± .4	88.8 ± 2.5
OX2	50.2 ± 5.5	1.3 ± .4	27.6 ± .5	7.4 ± .3	86.5 ± 5.7
RNAi	52.0 ± 1.6	1.7 ± .3	26.9 ± .5^*	7.7 ± .2	88.3 ± 1.3

Notes: Total indicates the sum of all constituent contents. Data represents mean ± SD of five biological replicates. The representation of statistical significance and plants are the same as in Figure 1.

Table 3. Yield and yield components of CRCT transgenic lines.

Plant	Straw (g DW)	Brown rice yield (g plant^−1)	Panicle number	Spikelet per panicle	Grain filling rate (%)	1000-grain weights (g)
NT	47.7 ± 3.9	25.2 ± 2.3	20.2 ± 3.1	66.3 ± 6.2	83.7 ± 4.3	22.8 ± .2
OX1	61.3 ± 3.2^**	14.3 ± .5^**	20.0 ± 1.6	61.5 ± 3.4	63.5 ± 2.5^**	18.5 ± .4^**
OX2	64.9 ± 6.8^**	10.8 ± 4.3^**	19.0 ± 2.0	56.8 ± 5.0^*	52.7 ± 16.2^*	18.6 ± 1.2^**
RNAi	46.3 ± 2.3	23.5 ± .9	24.8 ± 2.0^*	58.8 ± 5.8	77.3 ± 4.2	21.1 ± .2^**

Notes: Data represents mean ± SD of five biological replicates. The representation of statistical significance and plants are the same as in Figure 1.