Cellulose, a major constituent of plant biomass, is synthesized by a cellulose synthase complex.  It has been demonstrated that MYB genes transcriptionally regulate cellulose synthase in Arabidopsis.  However, little is known about this process in tomato.  Here, two MYB (SlMYB1/2) and three cellulose synthase (CESA) (SlCESA4/5/6) genes were isolated.  SlMYB1/2 and SlCESA4/5/6 accumulation was found to correspond to cellulose accumulation in different tissues of tomato.  Dual luciferase assays indicated that these two MYBs were transcriptional activators that interact with promoters of SlCESA4/5/6.  Moreover, SlMYB2 could also activate promoters of SlMYB1/2, suggesting the possible underlying auto-activation mechanisms for MYB transcription factors.  Transient over-expression of SlMYB1/2 in Nicotiana tabacum up-regulated tobacco endogenous NtCESA genes and increased cellulose accumulation.  The function of SlMYB1/2 was further investigated using stable transformation and the results indicated that N. tabacum lines heterologous expressing SlMYB1/2 displayed a pleiotropic phenotype, long and narrow leaves, with NtCESA induced and significant increase of cellulose.  In conclusion, our data suggest that tomato SlMYB1/2 have transcriptional regulatory roles in cellulose biosynthesis and SlMYB2 was more effective than SlMYB1, which may due to the transcriptional activation by SlMYB2 on SlMYB1 and itself.

Carbon sequestration in agricultural soils is a complex process controlled by farming practices, climate and some other environment factors. Since purple soils are unique in China and used as the main cropland in Sichuan Basin of China, it is of great importance to study and understand the impacts of different fertilizer amendments on soil organic carbon (SOC) changes with time. A research was carried out to investigate the relationship between soil carbon sequestration and organic carbon input as affected by different fertilizer treatments at two long-term rice-based cropping system experiments set up in early 1980s. Each experiment consisted of six identical treatments, including (1) no fertilizer (CK), (2) nitrogen and phosphorus fertilizers (NP), (3) nitrogen, phosphorus and potassium fertilizers (NPK), (4) fresh pig manure (M), (5) nitrogen and phosphorus fertilizers plus manure (MNP), and (6) nitrogen, phosphorus and potassium fertilizers plus manure (MNPK). The results showed that annual harvestable carbon biomass was the highest in the treatment of MNPK, followed by MNP and NPK, then M and NP, and the lowest in CK. Most of fertilizer treatments resulted in a significant gain in SOC ranging from 6.48 to 29.13% compared with the CK, and raised soil carbon sequestration rate to 0.10–0.53 t ha–1 yr−1. Especially, addition of manure on the basis of mineral fertilizers was very conducive to SOC maintenance in this soil. SOC content and soil carbon sequestration rate under balanced fertilizer treatments (NPK and MNPK) in the calcareous purple soil (Suining) were higher than that in the acid purple soil (Leshan). But carbon conversion rate at Leshan was 11.00%, almost 1.5 times of that (7.80%) at Suining. Significant linear correlations between soil carbon sequestration and carbon input were observed at both sites, signifying that the purple soil was not carbon-saturated and still had considerable potential to sequestrate more carbon.